cruk-pattern-library-api/patterns/collapsible.html

CRUK Pattern Library API

<div class="cr-collapsible">
    <input id="cr-collapsible__input-collapsible-box" class="cr-collapsible__input" type="checkbox">
    <label for="cr-collapsible__input-collapsible-box" class="cr-collapsible__heading-button">
        <h2 class="cr-collapsible__heading">
            This is collapsible box
        </h2>
    </label>
    <div class="cr-collapsible__content">
        Here are some content for collapsible box
    </div>
</div>