Dropdown

The official dropdown documentation is at http://materializecss.com/dropdown.html and below are some tips.

Borders/Dividers

The default dropdown does not include a visual separator between the options. But, by including an empty li element with the class of divider, you can achieve that.

<ul id="dropdown1" class="dropdown-content">
  <li><a href="#!">one</a></li>
  <li><a href="#!">two</a></li>
  <li class="divider"></li>
  <li><a href="#!">three</a></li>
</ul>

In this example that is taken from the official page, options two and three are separated by a 1px gray line.