How to make lists that open up when we hover over them?

#1

example
1.cars
1.1 american
1.1.1 nissan

i mean when we hover over cars american should show up
when we hover over american nissan should show up.

#2

See this example:

.show:hover ul.list-categories{
max-height: inherit;
opacity: 1;
}

.list-categories{
list-style-type: none;
padding: 0px;
margin: 0px;
max-height: 0px;
opacity: 0;
overflow: hidden;
transition: opacity 300ms ease;
}

<div class="show">show div
<ul class="list-categories">
  <li>Bed</li>
  <li>Bed</li>
  <li>Bed</li>
  <li>Bed</li>
  <li>Bed</li>
  <li>Bed</li>
</ul> 
</div>
#3

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