SOURCE

<div class="wrap">
  <div class="inner">
    <div class="box"></div>
  </div>
</div>

<div class="wrap2">
  <div class="inner2">
  </div>
</div>

.wrap{
  display:table;
}
.inner{
  display: table-cell;
  vertical-align: middle;
  width: 200px;
  height: 200px;
  border: 1px solid #ccc;
}
.box{
  width: 20px;
  height: 20px;
  border: 1px solid #ff0000
}


.wrap2{
  width: 200px;
  height: 200px;
  border: 1px solid #ff0000;
  display: inline;
  vertical-align: middle;
}
.inner2{
  width: 20px;
  height: 20px;
  border: 1px solid #ccc;
}