<div class="div1">
  <div class="div2"></div>
</div>

.div1 {
  width: 50px;
  height: 30px;
  position: relative;
  border: 1px solid green;
}

.div2 {
  width: 48px;
  height: 28px;
  position: absolute;
  border: 1px solid red;
}