<div class="father">
  <div class="son"></div>
</div>
.father {
  width: 200px;
  height: 200px;
  border: 1px solid #0a3b98;
  position: relative;
  background: skyblue;
}

.son {
  width: 100px;
  height: 100px;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  background: pink;
}
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