A CodePen by Sai Vineet. Dropdown Menu! - A simple dropdown menu in CSS3 using transitions.

index.html

<div id="container">
  <div class="slider" style="background:#B5E61D;">
    <button>lala</button>
  </div>
  <div class="slider"  style="background:#00A2E8;"></div>
  <div class="slider"  style="background:#4AD977;"></div>
  <div class="slider"  style="background:#FFC90E;"></div>
  <div class="slider"  style="background:#3F48CC;"></div>
</div>

script.js

$(function(){
  $('button').button();
})

style.css

#container{
  background-color:lime;
  width:57%;
  margin:0 auto;
  border-radius:5px;
}
.slider{
  width:100px;
  background-color:olive;
  height:1px;
  float:left;
  margin:10px;
  transition:all 0.5s;
  overflow:hidden;
  text-align:center;
  padding-top:20px;
  padding-bottom:0px;
    padding-left:0px;
    paddingright:0px;
}
.slider:hover{
 height:100px;
}