将一个块容器拉伸到与另一个块容器相同的高度

<div class="parent-container">
  <div class="block-container1">
    <!-- 内容1 -->
  </div>
  <div class="block-container2">
    <!-- 内容2 -->
  </div>
</div>

.parent-container {
  display: flex;
  align-items: stretch;
}

.block-container1, .block-container2 {
  flex: 1;
}

<div class="parent-container">
  <div class="block-container1">
    <!-- 内容1 -->
  </div>
  <div class="block-container2">
    <!-- 内容2 -->
  </div>
</div>

.parent-container {
  display: grid;
  grid-template-rows: auto 1fr;
}