diff --git a/gitlab-pages/docs/advanced/interop.md b/gitlab-pages/docs/advanced/interop.md
new file mode 100644
index 000000000..736efc8f8
--- /dev/null
+++ b/gitlab-pages/docs/advanced/interop.md
@@ -0,0 +1,730 @@
+---
+id: interop
+title: Interop
+---
+
+import Syntax from '@theme/Syntax';
+
+LIGO can work together with other smart contract languages on Tezos. However 
+data structures might have different representations in Michelson and not 
+correctly match the standard LIGO types. 
+
+## Michelson types and annotations
+Michelson types consist of `or`'s and `pair`'s, combined with field annotations.
+Field annotations add contraints on a Michelson type, for example a pair of 
+`(pair (int %foo) (string %bar))` will only work with the exact equivalence or 
+the same type without the field annotations.
+
+To clarify:
+
+```michelson
+(pair (int %foo) (string %bar))
+````
+
+works with 
+
+```michelson
+(pair (int %foo) (string %bar))
+```
+
+works with
+
+```michelson
+(pair int string)
+```
+
+works not with 
+
+```michelson
+(pair (int %bar) (string %foo))
+```
+
+works not with 
+
+```michelson
+(pair (string %bar) (int %foo))
+```
+
+:::info
+In the case of annotated entrypoints - the annotated `or` tree directly under 
+`parameter` in a contract - you should annotations, as otherwise it would 
+become unclear which entrypoint you are referring to.
+:::
+
+## Entrypoints and annotations
+It's possible for a contract to have multiple entrypoints, which translates in 
+LIGO to a `parameter` with a variant type as shown here:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+type storage is int
+
+type parameter is 
+ | Left of int
+ | Right of int
+
+function main (const p: parameter; const x: storage): (list(operation) * storage) is
+  ((nil: list(operation)), case p of
+  | Left(i) -> x - i
+  | Right(i) -> x + i
+  end)
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+type storage = int
+
+type parameter = 
+ | Left of int
+ | Right of int
+
+let main ((p, x): (parameter * storage)): (operation list * storage) = 
+  (([]: operation list), (match p with
+  | Left i -> x - i
+  | Right i -> x + i
+  ))
+
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+type storage = int
+
+type parameter = 
+ | Left(int)
+ | Right(int)
+
+let main = ((p, x): (parameter, storage)): (list(operation), storage) => {
+  ([]: list(operation), (switch(p) {
+  | Left(i) => x - i
+  | Right(i) => x + i
+  }))
+};
+
+```
+
+</Syntax>
+
+This contract can be called by another contract, like this one:
+
+
+<Syntax syntax="pascaligo">
+
+```pascaligo group=get_entrypoint_opt
+type storage is int
+
+type parameter is int
+
+type x is Left of int
+
+function main (const p: parameter; const s: storage): (list(operation) * storage) is block {
+  const contract: contract(x) = 
+    case (Tezos.get_entrypoint_opt("%left", ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx":address)): option(contract(x))) of 
+    | Some (c) -> c
+    | None -> (failwith("not a correct contract") : contract(x))
+    end;
+
+  const result: (list(operation) * storage) = ((list [Tezos.transaction(Left(2), 2mutez, contract)]: list(operation)), s)
+} with result
+```
+
+</Syntax>
+
+
+<Syntax syntax="cameligo">
+
+```cameligo group=get_entrypoint_opt
+type storage = int
+
+type parameter = int
+
+type x = Left of int
+
+let main (p, s: parameter * storage): operation list * storage = (
+  let contract: x contract = 
+    match ((Tezos.get_entrypoint_opt "%left" ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address)): x contract option) with
+    | Some c -> c
+    | None -> (failwith "contract does not match": x contract)
+  in  
+  (([
+    Tezos.transaction (Left 2) 2mutez contract;
+  ]: operation list), s)
+)
+```
+
+</Syntax>
+
+<Syntax syntax="reasonligo">
+
+```reasonligo group=get_entrypoint_opt
+type storage = int;
+
+type parameter = int;
+
+type x = Left(int);
+
+let main = ((p, s): (parameter, storage)): (list(operation), storage) => {
+  let contract: contract(x) = 
+    switch (Tezos.get_entrypoint_opt("%left", ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address)): option(contract(x))) {
+      | Some c => c
+      | None => (failwith ("contract does not match"): contract(x))
+    };
+  ([
+    Tezos.transaction(Left(2), 2mutez, contract)
+  ]: list(operation), s);
+};
+```
+
+</Syntax>
+
+Notice how we directly use the `%left` entrypoint without mentioning the 
+`%right` entrypoint. This is done with the help of annotations. Without 
+annotations it wouldn't be clear what our `int` would be referring to.
+
+This currently only works for `or`'s or variant types in LIGO.
+
+## Interop with Michelson
+To interop with existing Michelson code or for compatibility with certain 
+development tooling, LIGO has two special interop types: `michelson_or` and 
+`michelson_pair`. These types give the flexibility to model the exact Michelson
+output, including field annotations.
+
+Take for example the following Michelson type that we want to interop with:
+
+```michelson
+(or 
+  (unit %z)
+  (or %other 
+    (unit %y) 
+    (pair %other 
+      (string %x) 
+      (pair %other 
+        (int %w) 
+        (nat %v))))) 
+```  
+
+To reproduce this type we can use the following LIGO code:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+type w_and_v is michelson_pair(int, "w", nat, "v")
+type x_and is michelson_pair(string, "x", w_and_v, "other")
+type y_or is michelson_or(unit, "y", x_and, "other")
+type z_or is michelson_or(unit, "z", y_or, "other")
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+type w_and_v = (int, "w", nat, "v") michelson_pair
+type x_and = (string, "x", w_and_v, "other") michelson_pair
+type y_or = (unit, "y", x_and, "other") michelson_or
+type z_or = (unit, "z", y_or, "other") michelson_or
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+type w_and_v = michelson_pair(int, "w", nat, "v")
+type x_and = michelson_pair(string, "x", w_and_v, "other")
+type y_or = michelson_or(unit, "y", x_and, "other")
+type z_or = michelson_or(unit, "z", y_or, "other")
+```
+
+</Syntax>
+
+If you don't want to have an annotation, you need to provide an empty string.
+
+:::info
+Alternatively, if annotations are not important you can also use plain tuples
+for pair's instead. Plain tuples don't have any annotations.
+:::
+
+To use variables of type `michelson_or` you have to use `M_left` and `M_right`.
+`M_left` picks the left `or` case while `M_right` picks the right `or` case. 
+For `michelson_pair` you need to use tuples.
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+const z: z_or = (M_left (unit) : z_or);
+
+const y_1: y_or = (M_left (unit): y_or);
+const y: z_or = (M_right (y_1) : z_or);
+
+const x_pair: x_and = ("foo", (2, 3n));
+const x_1: y_or = (M_right (x_pair): y_or);
+const x: z_or = (M_right (y_1) : z_or);
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+let z: z_or = (M_left (unit) : z_or)
+
+let y_1: y_or = (M_left (unit): y_or)
+let y: z_or = (M_right (y_1) : z_or)
+
+let x_pair: x_and = ("foo", (2, 3n))
+let x_1: y_or = (M_right (x_pair): y_or)
+let x: z_or = (M_right (y_1) : z_or)
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+let z: z_or = (M_left (unit) : z_or)
+
+let y_1: y_or = (M_left (unit): y_or)
+let y: z_or = (M_right (y_1) : z_or)
+
+let x_pair: x_and = ("foo", (2, 3n))
+let x_1: y_or = (M_right (x_pair): y_or)
+let x: z_or = (M_right (y_1) : z_or)
+```
+
+</Syntax>
+
+## Helper functions
+Converting between different LIGO types and data structures can happen in two 
+ways. The first way is to use the provided layout conversion functions, and the 
+second way is to handle the layout conversion manually. 
+
+:::info
+In both cases it will increase the size of the smart contract and the 
+conversion will happen when running the smart contract.
+:::
+
+### Converting left combed Michelson data structures
+Here's an example of a left combed Michelson data structure using pairs: 
+
+```michelson
+ (pair %other 
+    (pair %other
+      (string %s)
+      (int %w)
+    )
+    (nat %v)
+  )
+```
+
+Which could respond with the following record type:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+type l_record is record [
+  s: string;
+  w: int;
+  v: nat
+]
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+type l_record = {
+  s: string;
+  w: int;
+  v: nat
+}
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+type l_record = {
+  s: string,
+  w: int,
+  v: nat
+}
+```
+
+</Syntax>
+
+If we want to convert from the Michelson type to our record type and vice 
+versa, we can use the following code:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+type michelson is michelson_pair_left_comb(l_record)
+
+function of_michelson (const f: michelson) : l_record is 
+  block {
+    const p: l_record = Layout.convert_from_left_comb(f)
+  } 
+  with p
+
+function to_michelson (const f: l_record) : michelson is 
+  block {
+    const p: michelson = Layout.convert_to_left_comb ((f: l_record))
+  }
+  with p
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+type michelson = l_record michelson_pair_left_comb
+
+let of_michelson (f: michelson) : l_record = 
+  let p: l_record = Layout.convert_from_left_comb f in
+  p
+
+let to_michelson (f: l_record) : michelson =
+  let p = Layout.convert_to_left_comb (f: l_record) in
+  p
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+type michelson = michelson_pair_left_comb(l_record);
+
+let of_michelson = (f: michelson) : l_record => { 
+  let p: l_record = Layout.convert_from_left_comb(f);
+  p
+};
+
+let to_michelson = (f: l_record) : michelson => {
+  let p = Layout.convert_to_left_comb(f: l_record);
+  p
+}
+
+```
+
+</Syntax>
+
+In the case of a left combed Michelson `or` data structure, that you want to 
+translate to a variant, you can use the `michelson_or_left_comb` type.
+
+For example:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+type vari is 
+| Foo of int
+| Bar of nat
+| Other of bool
+
+type r is michelson_or_left_comb(vari)
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+type vari = 
+| Foo of int
+| Bar of nat
+| Other of bool
+
+type r = vari michelson_or_left_comb
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+type vari = 
+| Foo(int)
+| Bar(nat)
+| Other(bool)
+
+type r = michelson_or_left_comb(vari)
+```
+
+</Syntax>
+
+And then use these types in `Layout.convert_from_left_comb` or 
+`Layout.convert_to_left_comb`, similar to the `pair`s example above, like this:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo
+function of_michelson_or (const f: r) : vari is 
+  block {
+    const p: vari = Layout.convert_from_left_comb(f)
+  } 
+  with p
+
+function to_michelson_or (const f: vari) : r is 
+  block {
+    const p: r = Layout.convert_to_left_comb((f: vari))
+  }
+  with p
+```
+
+</Syntax>
+<Syntax syntax="cameligo">
+
+```cameligo
+let of_michelson_or (f: r) : vari = 
+  let p: vari = Layout.convert_from_left_comb f in
+  p
+
+let to_michelson_or (f: vari) : r =
+  let p = Layout.convert_to_left_comb (f: vari) in
+  p
+```
+
+</Syntax>
+<Syntax syntax="reasonligo">
+
+```reasonligo
+let of_michelson_or = (f: r) : vari => { 
+  let p: vari = Layout.convert_from_left_comb(f);
+  p
+};
+
+let to_michelson_or = (f: vari) : r => {
+  let p = Layout.convert_to_left_comb(f: vari);
+  p
+}
+
+```
+
+</Syntax>
+
+### Converting right combed Michelson data structures
+
+In the case of right combed data structures, like:
+
+```michelson
+ (pair %other 
+    (string %s)
+    (pair %other
+      (int %w)    
+      (nat %v)
+    )
+  )
+```
+
+you can almost use the same code as that for the left combed data structures, 
+but with `michelson_or_right_comb`, `michelson_pair_right_comb`, 
+`Layout.convert_from_right_comb`, and `Layout.convert_to_left_comb` 
+respectively.
+
+### Manual data structure conversion
+If you want to get your hands dirty, it's also possible to do manual data 
+structure conversion.
+
+The following code can be used as inspiration:
+
+<Syntax syntax="pascaligo">
+
+```pascaligo group=helper_functions
+type z_to_v is
+| Z 
+| Y
+| X
+| W
+| V
+
+type w_or_v is michelson_or(unit, "w", unit, "v")
+type x_or is michelson_or(unit, "x", w_or_v, "other")
+type y_or is michelson_or(unit, "y", x_or, "other") 
+type z_or is michelson_or(unit, "z", y_or, "other") 
+
+type test is record [
+  z: string;
+  y: int;
+  x: string;
+  w: bool;
+  v: int;
+]
+
+function make_concrete_sum (const r: z_to_v) : z_or is block {
+  const z: z_or = (M_left (unit) : z_or);
+  
+  const y_1: y_or = (M_left (unit): y_or);
+  const y: z_or = (M_right (y_1) : z_or);
+
+  const x_2: x_or = (M_left (unit): x_or);
+  const x_1: y_or = (M_right (x_2): y_or);
+  const x: z_or = (M_right (x_1) : z_or);
+
+  const w_3: w_or_v = (M_left (unit): w_or_v);
+  const w_2: x_or = (M_right (w_3): x_or);
+  const w_1: y_or = (M_right (w_2): y_or);
+  const w: z_or = (M_right (w_1) : z_or);
+
+  const v_3: w_or_v = (M_right (unit): w_or_v);
+  const v_2: x_or = (M_right (v_3): x_or);
+  const v_1: y_or = (M_right (v_2): y_or);
+  const v: z_or = (M_right (v_1) : z_or);
+}
+ with (case r of 
+  | Z -> z
+  | Y -> y
+  | X -> x
+  | W -> w
+  | V -> v
+  end)
+
+
+function make_concrete_record (const r: test) : (string * int * string * bool * int) is
+  (r.z, r.y, r.x, r.w, r.v)  
+
+function make_abstract_sum (const z_or: z_or) : z_to_v is
+  (case z_or of
+  | M_left (n) -> Z
+  | M_right (y_or) -> 
+    (case y_or of
+    | M_left (n) -> Y
+    | M_right (x_or) ->
+        (case x_or of
+        | M_left (n) -> X
+        | M_right (w_or) ->
+            (case (w_or) of
+            | M_left (n) -> W
+            | M_right (n) -> V
+            end)
+        end)
+    end)
+  end)  
+
+function make_abstract_record (const z: string; const y: int; const x: string; const w: bool; const v: int) : test is
+  record [ z = z; y = y; x = x; w = w; v = v ]
+  
+```
+
+</Syntax>
+
+
+<Syntax syntax="cameligo">
+
+```cameligo group=helper_functions
+type z_to_v =
+| Z 
+| Y
+| X
+| W
+| V
+
+type w_or_v = (unit, "w", unit, "v") michelson_or
+type x_or = (unit, "x", w_or_v, "other") michelson_or
+type y_or = (unit, "y", x_or, "other") michelson_or
+type z_or = (unit, "z", y_or, "other") michelson_or
+
+type test = {
+  z: string;
+  y: int;
+  x: string;
+  w: bool;
+  v: int;
+}
+
+let make_concrete_sum (r: z_to_v) : z_or =
+  match r with 
+  | Z -> (M_left (unit) : z_or)
+  | Y -> (M_right (M_left (unit): y_or) : z_or )
+  | X -> (M_right (M_right (M_left (unit): x_or): y_or) : z_or )
+  | W -> (M_right (M_right (M_right (M_left (unit): w_or_v): x_or): y_or) : z_or )
+  | V -> (M_right (M_right (M_right (M_right (unit): w_or_v): x_or): y_or) : z_or )
+
+let make_concrete_record (r: test) : (string * int * string * bool * int) =
+  (r.z, r.y, r.x, r.w, r.v)  
+
+let make_abstract_sum (z_or: z_or) : z_to_v = 
+  match z_or with 
+  | M_left n -> Z
+  | M_right y_or -> 
+    (match y_or with 
+    | M_left n -> Y
+    | M_right x_or -> (
+        match x_or with 
+        | M_left n -> X
+        | M_right w_or -> (
+            match w_or with 
+            | M_left n -> W
+            | M_right n -> V)))
+
+
+let make_abstract_record (z: string) (y: int) (x: string) (w: bool) (v: int) : test =
+  { z = z; y = y; x = x; w = w; v = v }
+
+```
+
+</Syntax>
+
+<Syntax syntax="reasonligo">
+
+```reasonligo group=helper_functions
+type z_to_v =
+| Z 
+| Y
+| X
+| W
+| V
+
+type w_or_v = michelson_or(unit, "w", unit, "v")
+type x_or = michelson_or(unit, "x", w_or_v, "other")
+type y_or = michelson_or(unit, "y", x_or, "other")
+type z_or = michelson_or(unit, "z", y_or, "other")
+
+type test = {
+  z: string,
+  y: int,
+  x: string,
+  w: bool,
+  v: int
+}
+
+let make_concrete_sum = (r: z_to_v) : z_or =>
+  switch(r){
+  | Z => (M_left (unit) : z_or)
+  | Y => (M_right (M_left (unit): y_or) : z_or )
+  | X => (M_right (M_right (M_left (unit): x_or): y_or) : z_or )
+  | W => (M_right (M_right (M_right (M_left (unit): w_or_v): x_or): y_or) : z_or )
+  | V => (M_right (M_right (M_right (M_right (unit): w_or_v): x_or): y_or) : z_or )
+  }
+
+let make_concrete_record = (r: test) : (string, int, string, bool, int) =>
+  (r.z, r.y, r.x, r.w, r.v)  
+
+let make_abstract_sum = (z_or: z_or) : z_to_v =>
+  switch (z_or) {
+  | M_left n => Z
+  | M_right y_or => (
+    switch (y_or) {
+    | M_left n => Y
+    | M_right x_or => (
+        switch (x_or) {
+        | M_left n => X
+        | M_right w_or => (
+            switch (w_or) {
+            | M_left n => W
+            | M_right n => V
+            })
+        })
+    })
+  }
+
+
+let make_abstract_record = (z: string, y: int, x: string, w: bool, v: int) : test =>
+  { z : z, y, x, w, v }
+  
+```
+
+</Syntax>
+
+## Amendment
+With the upcoming 007 amendment to Tezos this will change though, and also 
+`pair`'s can be ordered differently.
\ No newline at end of file
diff --git a/gitlab-pages/website/sidebars.json b/gitlab-pages/website/sidebars.json
index 2d32e898b..7aef10a0e 100644
--- a/gitlab-pages/website/sidebars.json
+++ b/gitlab-pages/website/sidebars.json
@@ -19,8 +19,9 @@
       "advanced/entrypoints-contracts",
       "advanced/include",
       "advanced/first-contract",
-      "advanced/michelson-and-ligo",
-      "advanced/inline"
+      "advanced/michelson-and-ligo",      
+      "advanced/inline",
+      "advanced/interop"
     ],
     "Reference": [
       "api/cli-commands",
diff --git a/src/test/md_file_tests.ml b/src/test/md_file_tests.ml
index 3ceb8c3a6..57ad2d8b2 100644
--- a/src/test/md_file_tests.ml
+++ b/src/test/md_file_tests.ml
@@ -123,6 +123,7 @@ let md_files = [
   "/gitlab-pages/docs/advanced/entrypoints-contracts.md";
   "/gitlab-pages/docs/advanced/timestamps-addresses.md";
   "/gitlab-pages/docs/advanced/inline.md";
+  "/gitlab-pages/docs/advanced/interop.md";
   "/gitlab-pages/docs/api/cli-commands.md";
   "/gitlab-pages/docs/api/cheat-sheet.md";
   "/gitlab-pages/docs/reference/toplevel.md";