.parent { background: red; } .child { overflow: hidden; height: 0; background: blue; -webkit-transition: all .8s ease; -moz-transition: all .8s ease; -ms-transition: all .8s ease; -o-transition: all .8s ease; transition: all .8s ease; color: white; } .parent:hover > .child { height: 30px; display: block; }
cascade style sheet