HTML

  
  <p>Desarrollo de software</p>
  <select name="lenguajes">
    <option value="">Selecciona una opción</option>
    <optgroup label="Frontend">
      <option value="html">HTML</option>
      <option value="css">CSS</option>
      <option value="js">JavaScript</option>
    </optgroup>
    <optgroup label="Backend">
      <option value="php">PHP</option>
      <option value="ruby">Ruby</option>
      <option value="py">Python</option>
    </optgroup>
    <optgroup label="Tecnologías">
      <option value="aws">AWS</option>
      <option value="docker">Docker</option>
      <option value="host">Hosting</option>
    </optgroup>
  </select>
  

CSS

  
    select {
      width: 50%;
      padding: 8px;
      margin: 1rem 0;
      border: none;
      box-shadow: black 0 0 4px;
    }