display block element animation code example
Example: 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>