schema.js

const Post = new GraphQLObjectType({
  name: 'Post',
  fields: () => ({
    id: {type: GraphQLString},
    title: {type: GraphQLString},
    author: {type: Author},
  })
});

const Author = new GraphQLObjectType({
  name: 'Author',
  fields: () => ({
    id: {type: GraphQLString},
    name: {type: GraphQLString},
  })
});

const RootQuery = new GraphQLObjectType({
  name: 'RootQuery',
  fields: () => ({
    recentPost: {
      type: Post,
      resolve(root, args, info) {
        ....
      }
    }
  })
});

const schema = new GraphQLSchema({
  query: RootQuery
});