using css transition code example

Example 1: display transition css

div {
  background-color: blue;
  padding: 40px;
  color: white;
  cursor: pointer;
  transition: all .1s ease;
}

.hidden {
  visibility: hidden;
  opacity: 0;
  max-height: 0%;
}

.hidden:hover {
  visibility: visible;
  opacity: 1;
  max-height: 1000px;
}
<div class="hidden"></div>

Example 2: css transition

/*CSS Transition Syntax*/
selector {
 transition: property duration timing-function delay|initial|inherit; 
}