Submenu

index.html

<div class="menu">
	<div class="menu__item">Foo
		<div class="menu menu_submenu">
			<div class="menu__item">Foo</div>
			<div class="menu__item">Bar</div>
			<div class="menu__item">Baz</div>
		</div>
	</div>
	<div class="menu__item">Bar</div>
	<div class="menu__item">Baz</div>
</div>

index.styl

.menu
	&__item
		display: inline-block
		color: red
		
	&_submenu
		display: none
		position: absolute

	&__item:hover &_submenu
		display: block

	&_submenu &__item
		color: blue