SOURCE

<div class="container">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
  <div class="item">5</div>
</div>

.container {
  width: 600px;
  background: #fff;
  di
  .item {
    width: 300px;
    height: 200px;
    border: 10px solid #fff;
    background: grey;
    float: left;
    box-sizing: border-box;
    color: #fff;
    text-align: center;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 26px;
    &:hover {
      height: 300px;
    }
    transition: all .5s;
  }
}

.clearfix:after {
  visibility: hidden;
  display: block;
  font-size: 0;
  content: " ";
  clear: both;
  height: 0;
}