body {
  width: 900px;
  height: 500px;
  border: dotted 1px green;
}

.wrapper {
  border: solid 1px blue;
  width: 600px;
  display: block;
  line-height: 300px;
}

.subDiv {
  border: solid 1px red;
  width: 100px;
  vertical-align: middle;
  height: 100px;
  display: inline-block;
}