<div class="left">
<div class="item">
    <span class="glyphicon glyphicon-th-large"><img src="assets/icon/sidebar/dashboard.png"></span>

</div>
<div class="item active">
    <span class="glyphicon glyphicon-th-list"></span>
</div>
<div class="item">
    <span class="glyphicon glyphicon-log-out"></span>
</div>

.left, .right {
        float:left;
        height:100vh;
    }

.left {
        background: #3B3B3B;
        display: inline-block;
        white-space: nowrap;
        width: 50px;
        transition: width 1s ;
    }

.left:hover {
        width: 170px;
    }

.item:hover {
        background-color:#ccc;
        }