有情况如下：三个div的高度是随着内容自适应的，但希望每列的高度都相同，即，都与最高的相同。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.container {
display: flex;
justify-content: space-between;
}
.item {
width: 100px;
}
.aqua {
background-color: rgb(97, 231, 231);
}
.green {
background-color: rgb(135, 226, 150);
}
.yellow {
background-color: rgb(240, 240, 131);
}
</style>
</head>
<body>
<div class="container">
<div class="item aqua">
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
</div>
<div class="item">
<div class="item1 green">
<p>2</p>
</div>
<div class="item1 yellow">
<p>2</p>
<p>2</p>
</div>
</div>
<div class="item">
<div class="item1 green">
<p>2</p>
</div>
<div class="item1 yellow">
<p>2</p>
<p>2</p>
</div>
<div class="item aqua">
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
</div>
</div>
</div>
</body>
</html>
实现方法：令父元素flex，且align-items: stretch;
想要让子元素下面的元素贴底，可以令子元素：
display: flex;
flex-direction: column;
justify-content: space-between;
可以把这段css放到一个新的类里，命名为alignHeight，在任何想要实现此效果的div中加入此类。
修改后的代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.container {
display: flex;
justify-content: space-between;
align-items: stretch;
}
.alignHeight {
display: flex;
flex-direction: column;
justify-content: space-between;
}
.item {
width: 100px;
}
.aqua {
background-color: rgb(97, 231, 231);
}
.green {
background-color: rgb(135, 226, 150);
}
.yellow {
background-color: rgb(240, 240, 131);
}
</style>
</head>
<body>
<div class="container">
<div class="item aqua alignHeight">
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
</div>
<div class="item alignHeight">
<div class="item1 green">
<p>2</p>
</div>
<div class="item1 yellow">
<p>2</p>
<p>2</p>
</div>
</div>
<div class="item alignHeight">
<div class="item1 green">
<p>2</p>
</div>
<div class="item1 yellow">
<p>2</p>
<p>2</p>
</div>
<div class="item aqua">
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
</div>
</div>
</div>
</body>
</html>