diff --git a/src/data/openalex-fields.json.ts b/src/data/openalex-fields.json.ts
index d569443..c6330dd 100644
--- a/src/data/openalex-fields.json.ts
+++ b/src/data/openalex-fields.json.ts
@@ -2,7 +2,7 @@ import { HttpClient, Terminal } from '@effect/platform'
 import { NodeTerminal } from '@effect/platform-node'
 import { Schema } from '@effect/schema'
 import { Effect, Record } from 'effect'
-import { FieldIdFromUrlSchema, FieldIdSchema } from '../lib/OpenAlex.js'
+import { DomainIdFromUrlSchema, DomainIdSchema, FieldIdFromUrlSchema, FieldIdSchema } from '../lib/OpenAlex.js'
 import { UrlFromStringSchema } from '../lib/Url.js'
 
 const Fields = Schema.Struct({
@@ -10,11 +10,14 @@ const Fields = Schema.Struct({
     Schema.Struct({
       id: Schema.compose(UrlFromStringSchema, FieldIdFromUrlSchema),
       display_name: Schema.String,
+      domain: Schema.Struct({
+        id: Schema.compose(UrlFromStringSchema, DomainIdFromUrlSchema),
+      }),
     }),
   ),
 })
 
-const FieldNames = Schema.Record(FieldIdSchema, Schema.String)
+const FieldNames = Schema.Record(FieldIdSchema, Schema.Struct({ name: Schema.String, domain: DomainIdSchema }))
 
 const program = Effect.gen(function* () {
   const terminal = yield* Terminal.Terminal
@@ -25,7 +28,10 @@ const program = Effect.gen(function* () {
     .fetchOk(request)
     .pipe(Effect.andThen(HttpClient.response.schemaBodyJson(Fields)), Effect.scoped)
 
-  const transformedData = Record.fromIterableWith(data.results, field => [field.id, field.display_name])
+  const transformedData = Record.fromIterableWith(data.results, field => [
+    field.id,
+    { name: field.display_name, domain: field.domain.id },
+  ])
 
   const encoded = yield* Schema.encode(Schema.parseJson(FieldNames))(transformedData)
 
diff --git a/src/data/requests.json.ts b/src/data/requests.json.ts
index 198356a..4424ab5 100644
--- a/src/data/requests.json.ts
+++ b/src/data/requests.json.ts
@@ -3,7 +3,7 @@ import { NodeTerminal } from '@effect/platform-node'
 import { Schema } from '@effect/schema'
 import { Effect } from 'effect'
 import * as LanguageCode from '../lib/LanguageCode.js'
-import { FieldIdSchema } from '../lib/OpenAlex.js'
+import { DomainIdSchema, FieldIdSchema } from '../lib/OpenAlex.js'
 import * as Temporal from '../lib/Temporal.js'
 
 const Requests = Schema.Array(
@@ -11,6 +11,7 @@ const Requests = Schema.Array(
     timestamp: Temporal.InstantFromStringSchema,
     language: Schema.optional(LanguageCode.LanguageCodeSchema, { nullable: true }),
     fields: Schema.Array(FieldIdSchema),
+    domains: Schema.Array(DomainIdSchema),
   }),
 )
 
diff --git a/src/lib/OpenAlex.ts b/src/lib/OpenAlex.ts
index 0c12c5d..c8d0312 100644
--- a/src/lib/OpenAlex.ts
+++ b/src/lib/OpenAlex.ts
@@ -15,3 +15,17 @@ export const FieldIdFromUrlSchema = Schema.transformOrFail(UrlFromSelfSchema, Fi
       : Either.left(new ParseResult.Type(ast, url)),
   encode: topicId => ParseResult.succeed(new URL(`https://openalex.org/fields/${encodeURIComponent(topicId)}`)),
 })
+
+type DomainId = string & Brand.Brand<'OpenAlexDomainId'>
+
+const DomainId = Brand.nominal<DomainId>()
+
+export const DomainIdSchema = Schema.String.pipe(Schema.fromBrand(DomainId))
+
+export const DomainIdFromUrlSchema = Schema.transformOrFail(UrlFromSelfSchema, DomainIdSchema, {
+  decode: (url, _, ast) =>
+    url.origin === 'https://openalex.org' && url.pathname.startsWith('/domains/')
+      ? Either.right(decodeURIComponent(url.pathname.substring(9)))
+      : Either.left(new ParseResult.Type(ast, url)),
+  encode: topicId => ParseResult.succeed(new URL(`https://openalex.org/domains/${encodeURIComponent(topicId)}`)),
+})
diff --git a/src/requests.md b/src/requests.md
index c8f88f9..7ae8d58 100644
--- a/src/requests.md
+++ b/src/requests.md
@@ -42,7 +42,7 @@ const languageColor = Plot.scale({
 })
 
 const requestsByField = requests.flatMap(({ fields, ...request }) =>
-  fields.map(field => ({ ...request, field: openAlexFields[field] })),
+  fields.map(field => ({ ...request, field: openAlexFields[field].name })),
 )
 ```