Essayez-le vous-même - W3.CSS ref

<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="/lib/w3.css">

<h2>Accordions</h2>
<p>Click on the buttons to show the collapsible content. Click it again to hide it.</p>

<div class="w3-accordion w3-light-grey">
  <button onclick="myFunction('Demo1')" class="w3-btn-block w3-left-align">Open Content 1</button>
  <div id="Demo1" class="w3-accordion-content">
    <div class="w3-container">
      <p>Some text..</p>
    </div>
  </div>
  <button onclick="myFunction('Demo2')" class="w3-btn-block w3-left-align">Open Content 2</button>
  <div id="Demo2" class="w3-accordion-content">
    <a href="#">Link 1</a>
    <a href="#">Link 2</a>
    <a href="#">Link 3</a>
  </div>
</div>

</body>
</html>