A CodePen by Derek P. Collins. Basic Popover Animation - Popover slides up and fades in on hover of an element. Just CSS, no JavaScript.

index.html

<div class="center">
  <span class="qs">? <span class="popover above">Hey bro, cool popover.</span></span>
</div>

style.scss

@import "compass";
body {
  background-color: #e3fbff;
}
/* Just to center things */
.center {
  margin: 100px auto;
  width: 30px;
}

/* The element to hover over */
.qs {
  background-color: #02bdda;
  border-radius: 16px;
  color: #e3fbff;
  cursor: default;
  display: inline-block;
  font-family: 'Helvetica',sans-serif;
  font-size: 18px;
  font-weight: bold;
  height: 30px;
  line-height: 30px;
  position: relative;
  text-align: center;
  width: 30px;
  
  .popover {
    background-color: rgba(0,0,0,0.85);
    border-radius: 5px;
    bottom: 42px;
    box-shadow: 0 0 5px rgba(0,0,0,0.4);
    color: #fff;
    display: none;
    font-size: 12px;
    font-family: 'Helvetica',sans-serif;
    left: -95px;
    padding: 7px 10px;
    position: absolute;
    width: 200px;
    z-index: 4;
    
    &:before {
        border-top: 7px solid rgba(0,0,0,0.85);
        border-right: 7px solid transparent;
        border-left: 7px solid transparent;
        bottom: -7px;
        content: '';
        display: block;
        left: 50%;
        margin-left: -7px;
        position: absolute;
      }
  }
  
  &:hover {
      .popover {
        display: block;
        -webkit-animation: fade-in .3s linear 1, move-up .3s linear 1;
        -moz-animation: fade-in .3s linear 1, move-up .3s linear 1;
        -ms-animation: fade-in .3s linear 1, move-up .3s linear 1;
      }
    }
}

@-webkit-keyframes fade-in {
	from   { opacity: 0; }
	to { opacity: 1; }
}
@-moz-keyframes fade-in {
	from   { opacity: 0; }
	to { opacity: 1; }
}
@-ms-keyframes fade-in {
	from   { opacity: 0; }
	to { opacity: 1; }
}
@-webkit-keyframes move-up {
	from   { bottom: 30px; }
	to { bottom: 42px; }
}
@-moz-keyframes move-up {
	from   { bottom: 30px; }
	to { bottom: 42px; }
}
@-ms-keyframes move-up {
	from   { bottom: 30px; }
	to { bottom: 42px; }
}