diff --git a/src/generic/Loading.jsx b/src/generic/Loading.jsx
index 7f109a245c..9c696b013c 100644
--- a/src/generic/Loading.jsx
+++ b/src/generic/Loading.jsx
@@ -2,27 +2,24 @@ import React from 'react';
 import { Spinner } from '@edx/paragon';
 import { FormattedMessage } from '@edx/frontend-platform/i18n';
 
+export const LoadingSpinner = () => (
+  <Spinner
+    animation="border"
+    role="status"
+    variant="primary"
+    screenReaderText={(
+      <FormattedMessage
+        id="authoring.loading"
+        defaultMessage="Loading..."
+        description="Screen-reader message for when a page is loading."
+      />
+    )}
+  />
+);
+
 const Loading = () => (
-  <div
-    className="d-flex justify-content-center align-items-center flex-column"
-    style={{
-      height: '100vh',
-    }}
-  >
-    <Spinner
-      animation="border"
-      role="status"
-      variant="primary"
-      screenReaderText={(
-        <span className="sr-only">
-          <FormattedMessage
-            id="authoring.loading"
-            defaultMessage="Loading..."
-            description="Screen-reader message for when a page is loading."
-          />
-        </span>
-      )}
-    />
+  <div className="d-flex justify-content-center align-items-center flex-column vh-100">
+    <LoadingSpinner />
   </div>
 );
 
diff --git a/src/generic/utils.js b/src/generic/utils.js
index 27236e8aa8..c24e5a1646 100644
--- a/src/generic/utils.js
+++ b/src/generic/utils.js
@@ -1,10 +1,16 @@
 import { isEmpty } from 'lodash';
 
-const getPageHeadTitle = (courseName, pageName) => {
-  if (isEmpty(courseName)) {
+/**
+ * Generate the string for the page <title>
+ * @param {string} courseOrSectionName The name of the course, or the section of the MFE that the user is in currently
+ * @param {string} pageName The name of the current page
+ * @returns {string} The combined title
+ */
+const getPageHeadTitle = (courseOrSectionName, pageName) => {
+  if (isEmpty(courseOrSectionName)) {
     return `${pageName} | ${process.env.SITE_NAME}`;
   }
-  return `${pageName} | ${courseName} | ${process.env.SITE_NAME}`;
+  return `${pageName} | ${courseOrSectionName} | ${process.env.SITE_NAME}`;
 };
 
 export default getPageHeadTitle;
diff --git a/src/taxonomy/TaxonomyListPage.jsx b/src/taxonomy/TaxonomyListPage.jsx
index 79ca9982aa..20287b693f 100644
--- a/src/taxonomy/TaxonomyListPage.jsx
+++ b/src/taxonomy/TaxonomyListPage.jsx
@@ -6,7 +6,10 @@ import {
   Spinner,
 } from '@edx/paragon';
 import { useIntl } from '@edx/frontend-platform/i18n';
+import { Helmet } from 'react-helmet';
+
 import SubHeader from '../generic/sub-header/SubHeader';
+import getPageHeadTitle from '../generic/utils';
 import messages from './messages';
 import TaxonomyCard from './taxonomy-card';
 import { useTaxonomyListDataResponse, useIsTaxonomyListDataLoaded } from './data/apiHooks';
@@ -35,6 +38,9 @@ const TaxonomyListPage = () => {
 
   return (
     <>
+      <Helmet>
+        <title>{getPageHeadTitle('', intl.formatMessage(messages.headerTitle))}</title>
+      </Helmet>
       <div className="pt-4.5 pr-4.5 pl-4.5 pb-2 bg-light-100 box-shadow-down-2">
         <Container size="xl">
           <SubHeader
diff --git a/src/taxonomy/data/api.js b/src/taxonomy/data/api.js
index 94dd0af7c6..126f272356 100644
--- a/src/taxonomy/data/api.js
+++ b/src/taxonomy/data/api.js
@@ -7,6 +7,7 @@ const getApiBaseUrl = () => getConfig().STUDIO_BASE_URL;
 export const getTaxonomyListApiUrl = (org) => {
   const url = new URL('api/content_tagging/v1/taxonomies/', getApiBaseUrl());
   url.searchParams.append('enabled', 'true');
+  url.searchParams.append('page_size', '500'); // For the tagging MVP, we don't paginate the taxonomy list
   if (org !== undefined) {
     url.searchParams.append('org', org);
   }
diff --git a/src/taxonomy/tag-list/TagListTable.jsx b/src/taxonomy/tag-list/TagListTable.jsx
index 09a6a26d63..2fa3c042a0 100644
--- a/src/taxonomy/tag-list/TagListTable.jsx
+++ b/src/taxonomy/tag-list/TagListTable.jsx
@@ -1,14 +1,46 @@
 // ts-check
-import { useIntl } from '@edx/frontend-platform/i18n';
-import {
-  DataTable,
-} from '@edx/paragon';
+import { FormattedMessage, useIntl } from '@edx/frontend-platform/i18n';
+import { DataTable } from '@edx/paragon';
 import _ from 'lodash';
 import Proptypes from 'prop-types';
 import { useState } from 'react';
 
+import { LoadingSpinner } from '../../generic/Loading';
 import messages from './messages';
 import { useTagListDataResponse, useTagListDataStatus } from './data/apiHooks';
+import { useSubTags } from './data/api';
+
+const SubTagsExpanded = ({ taxonomyId, parentTagValue }) => {
+  const subTagsData = useSubTags(taxonomyId, parentTagValue);
+
+  if (subTagsData.isLoading) {
+    return <LoadingSpinner />;
+  }
+  if (subTagsData.isError) {
+    return <FormattedMessage {...messages.tagListError} />;
+  }
+
+  return (
+    <ul style={{ listStyleType: 'none' }}>
+      {subTagsData.data.results.map(tagData => (
+        <li key={tagData.id} style={{ paddingLeft: `${(tagData.depth - 1) * 30}px` }}>
+          {tagData.value} <span className="text-light-900">{tagData.childCount > 0 ? `(${tagData.childCount})` : null}</span>
+        </li>
+      ))}
+    </ul>
+  );
+};
+
+SubTagsExpanded.propTypes = {
+  taxonomyId: Proptypes.number.isRequired,
+  parentTagValue: Proptypes.string.isRequired,
+};
+
+/**
+ * An "Expand" toggle to show/hide subtags, but one which is hidden if the given tag row has no subtags.
+ */
+const OptionalExpandLink = ({ row }) => (row.values.childCount > 0 ? <DataTable.ExpandRow row={row} /> : null);
+OptionalExpandLink.propTypes = DataTable.ExpandRow.propTypes;
 
 const TagListTable = ({ taxonomyId }) => {
   const intl = useIntl();
@@ -34,11 +66,24 @@ const TagListTable = ({ taxonomyId }) => {
       itemCount={tagList?.count || 0}
       pageCount={tagList?.numPages || 0}
       initialState={options}
+      isExpandable
+      // This is a temporary "bare bones" solution for brute-force loading all the child tags. In future we'll match
+      // the Figma design and do something more sophisticated.
+      renderRowSubComponent={({ row }) => <SubTagsExpanded taxonomyId={taxonomyId} parentTagValue={row.values.value} />}
       columns={[
         {
           Header: intl.formatMessage(messages.tagListColumnValueHeader),
           accessor: 'value',
         },
+        {
+          id: 'expander',
+          Header: DataTable.ExpandAll,
+          Cell: OptionalExpandLink,
+        },
+        {
+          Header: intl.formatMessage(messages.tagListColumnChildCountHeader),
+          accessor: 'childCount',
+        },
       ]}
     >
       <DataTable.TableControlBar />
@@ -50,7 +95,7 @@ const TagListTable = ({ taxonomyId }) => {
 };
 
 TagListTable.propTypes = {
-  taxonomyId: Proptypes.string.isRequired,
+  taxonomyId: Proptypes.number.isRequired,
 };
 
 export default TagListTable;
diff --git a/src/taxonomy/tag-list/TagListTable.test.jsx b/src/taxonomy/tag-list/TagListTable.test.jsx
index e9d5015dd4..dd79c107fa 100644
--- a/src/taxonomy/tag-list/TagListTable.test.jsx
+++ b/src/taxonomy/tag-list/TagListTable.test.jsx
@@ -1,29 +1,84 @@
 import React from 'react';
 import { IntlProvider } from '@edx/frontend-platform/i18n';
+import { getAuthenticatedHttpClient } from '@edx/frontend-platform/auth';
 import { initializeMockApp } from '@edx/frontend-platform';
 import { AppProvider } from '@edx/frontend-platform/react';
-import { render } from '@testing-library/react';
+import { render, waitFor } from '@testing-library/react';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import MockAdapter from 'axios-mock-adapter';
 
-import { useTagListData } from './data/api';
 import initializeStore from '../../store';
 import TagListTable from './TagListTable';
 
 let store;
-
-jest.mock('./data/api', () => ({
-  useTagListData: jest.fn(),
-}));
+let axiosMock;
+const queryClient = new QueryClient();
 
 const RootWrapper = () => (
   <AppProvider store={store}>
     <IntlProvider locale="en" messages={{}}>
-      <TagListTable taxonomyId="1" />
+      <QueryClientProvider client={queryClient}>
+        <TagListTable taxonomyId={1} />
+      </QueryClientProvider>
     </IntlProvider>
   </AppProvider>
 );
 
-describe('<TagListPage />', async () => {
-  beforeEach(async () => {
+const tagDefaults = { depth: 0, external_id: null, parent_value: null };
+const mockTagsResponse = {
+  next: null,
+  previous: null,
+  count: 3,
+  num_pages: 1,
+  current_page: 1,
+  start: 0,
+  results: [
+    {
+      ...tagDefaults,
+      value: 'two level tag 1',
+      child_count: 1,
+      _id: 1001,
+      sub_tags_url: '/request/to/load/subtags/1',
+    },
+    {
+      ...tagDefaults,
+      value: 'two level tag 2',
+      child_count: 1,
+      _id: 1002,
+      sub_tags_url: '/request/to/load/subtags/2',
+    },
+    {
+      ...tagDefaults,
+      value: 'two level tag 3',
+      child_count: 1,
+      _id: 1003,
+      sub_tags_url: '/request/to/load/subtags/3',
+    },
+  ],
+};
+const rootTagsListUrl = 'http://localhost:18010/api/content_tagging/v1/taxonomies/1/tags/?page=1';
+const subTagsResponse = {
+  next: null,
+  previous: null,
+  count: 1,
+  num_pages: 1,
+  current_page: 1,
+  start: 0,
+  results: [
+    {
+      ...tagDefaults,
+      depth: 1,
+      value: 'the child tag',
+      child_count: 0,
+      _id: 1111,
+      sub_tags_url: null,
+    },
+  ],
+};
+const subTagsUrl = 'http://localhost:18010/api/content_tagging/v1/taxonomies/1/tags/?full_depth_threshold=10000&parent_tag=two+level+tag+1';
+
+describe('<TagListPage />', () => {
+  beforeAll(async () => {
     initializeMockApp({
       authenticatedUser: {
         userId: 3,
@@ -32,36 +87,45 @@ describe('<TagListPage />', async () => {
         roles: [],
       },
     });
+    axiosMock = new MockAdapter(getAuthenticatedHttpClient());
+  });
+  beforeEach(async () => {
     store = initializeStore();
+    axiosMock.reset();
   });
 
   it('shows the spinner before the query is complete', async () => {
-    useTagListData.mockReturnValue({
-      isLoading: true,
-      isFetched: false,
-    });
-    const { getByRole } = render(<RootWrapper />);
-    const spinner = getByRole('status');
+    // Simulate an actual slow response from the API:
+    let resolveResponse;
+    const promise = new Promise(resolve => { resolveResponse = resolve; });
+    axiosMock.onGet(rootTagsListUrl).reply(() => promise);
+    const result = render(<RootWrapper />);
+    const spinner = result.getByRole('status');
     expect(spinner.textContent).toEqual('loading');
+    resolveResponse([200, {}]);
+    await waitFor(() => {
+      expect(result.getByText('No results found')).toBeInTheDocument();
+    });
   });
 
   it('should render page correctly', async () => {
-    useTagListData.mockReturnValue({
-      isSuccess: true,
-      isFetched: true,
-      isError: false,
-      data: {
-        count: 3,
-        numPages: 1,
-        results: [
-          { value: 'Tag 1' },
-          { value: 'Tag 2' },
-          { value: 'Tag 3' },
-        ],
-      },
+    axiosMock.onGet(rootTagsListUrl).reply(200, mockTagsResponse);
+    const result = render(<RootWrapper />);
+    await waitFor(() => {
+      expect(result.getByText('two level tag 1')).toBeInTheDocument();
     });
-    const { getAllByRole } = render(<RootWrapper />);
-    const rows = getAllByRole('row');
+    const rows = result.getAllByRole('row');
     expect(rows.length).toBe(3 + 1); // 3 items plus header
   });
+
+  it('should render page correctly with subtags', async () => {
+    axiosMock.onGet(rootTagsListUrl).reply(200, mockTagsResponse);
+    axiosMock.onGet(subTagsUrl).reply(200, subTagsResponse);
+    const result = render(<RootWrapper />);
+    const expandButton = result.getAllByLabelText('Expand row')[0];
+    expandButton.click();
+    await waitFor(() => {
+      expect(result.getByText('the child tag')).toBeInTheDocument();
+    });
+  });
 });
diff --git a/src/taxonomy/tag-list/data/api.js b/src/taxonomy/tag-list/data/api.js
index 570e29ce48..6561256e9a 100644
--- a/src/taxonomy/tag-list/data/api.js
+++ b/src/taxonomy/tag-list/data/api.js
@@ -25,3 +25,22 @@ export const useTagListData = (taxonomyId, options) => {
     },
   });
 };
+
+/**
+ * Temporary hook to load *all* the subtags of a given tag in a taxonomy.
+ * Doesn't handle pagination or anything. This is meant to be replaced by
+ * something more sophisticated later, as we improve the "taxonomy details" page.
+ * @param {number} taxonomyId
+ * @param {string} parentTagValue
+ * @returns {import('@tanstack/react-query').UseQueryResult<import('./types.mjs').TagData>}
+ */
+export const useSubTags = (taxonomyId, parentTagValue) => useQuery({
+  queryKey: ['subtagsList', taxonomyId, parentTagValue],
+  queryFn: async () => {
+    const url = new URL(`api/content_tagging/v1/taxonomies/${taxonomyId}/tags/`, getApiBaseUrl());
+    url.searchParams.set('full_depth_threshold', '10000'); // Load as deeply as we can
+    url.searchParams.set('parent_tag', parentTagValue);
+    const response = await getAuthenticatedHttpClient().get(url.href);
+    return camelCaseObject(response.data);
+  },
+});
diff --git a/src/taxonomy/tag-list/messages.js b/src/taxonomy/tag-list/messages.js
index 5832fdb465..82db9caba7 100644
--- a/src/taxonomy/tag-list/messages.js
+++ b/src/taxonomy/tag-list/messages.js
@@ -9,6 +9,14 @@ const messages = defineMessages({
     id: 'course-authoring.tag-list.column.value.header',
     defaultMessage: 'Value',
   },
+  tagListColumnChildCountHeader: {
+    id: 'course-authoring.tag-list.column.value.header',
+    defaultMessage: '# child tags',
+  },
+  tagListError: {
+    id: 'course-authoring.tag-list.error',
+    defaultMessage: 'Error: unable to load child tags',
+  },
 });
 
 export default messages;
diff --git a/src/taxonomy/taxonomy-detail/TaxonomyDetailPage.jsx b/src/taxonomy/taxonomy-detail/TaxonomyDetailPage.jsx
index a22fb0bd57..177bac326d 100644
--- a/src/taxonomy/taxonomy-detail/TaxonomyDetailPage.jsx
+++ b/src/taxonomy/taxonomy-detail/TaxonomyDetailPage.jsx
@@ -6,10 +6,12 @@ import {
   Container,
   Layout,
 } from '@edx/paragon';
+import { Helmet } from 'react-helmet';
 import { Link, useParams } from 'react-router-dom';
 
 import ConnectionErrorAlert from '../../generic/ConnectionErrorAlert';
 import Loading from '../../generic/Loading';
+import getPageHeadTitle from '../../generic/utils';
 import SubHeader from '../../generic/sub-header/SubHeader';
 import taxonomyMessages from '../messages';
 import TaxonomyDetailMenu from './TaxonomyDetailMenu';
@@ -20,9 +22,12 @@ import { useTaxonomyDetailDataResponse, useTaxonomyDetailDataStatus } from './da
 
 const TaxonomyDetailPage = () => {
   const intl = useIntl();
-  const { taxonomyId } = useParams();
-  const { isError, isFetched } = useTaxonomyDetailDataStatus(taxonomyId);
+  const { taxonomyId: taxonomyIdString } = useParams();
+  const taxonomyId = Number(taxonomyIdString);
+
   const taxonomy = useTaxonomyDetailDataResponse(taxonomyId);
+  const { isError, isFetched } = useTaxonomyDetailDataStatus(taxonomyId);
+
   const [isExportModalOpen, setIsExportModalOpen] = useState(false);
 
   if (!isFetched) {
@@ -74,6 +79,9 @@ const TaxonomyDetailPage = () => {
 
   return (
     <>
+      <Helmet>
+        <title>{getPageHeadTitle(intl.formatMessage(taxonomyMessages.headerTitle), taxonomy.name)}</title>
+      </Helmet>
       <div className="pt-4.5 pr-4.5 pl-4.5 pb-2 bg-light-100 box-shadow-down-2">
         <Container size="xl">
           <Breadcrumb