align-self属性允许单个项目有与其他项目不一样的对齐方式，可覆盖align-items属性。默认值为auto，表示继承父元素的align-items属性，如果没有父元素，则等同于stretch,
用法：
div span:nth-child(3) {
align-self: flex-end;
}

例子

  1. <!DOCTYPE html>
  2. <html lang="en">
  4. <head>
  5.   <meta charset="UTF-8">
  6.   <meta http-equiv="X-UA-Compatible" content="IE=edge">
  7.   <meta name="viewport" content="width=device-width, initial-scale=1.0">
  8.   <title>Document</title>
  10.   <style>
  11.     div {
  12.       display: flex;
  13.       width: 500px;
  14.       height: 200px;
  15.       background-color: blue;
  16.       justify-content: center;
  17.     }
  19.     div span {
  20.       width: 100px;
  21.       height: 100px;
  22.       background-color: red;
  23.     }
  25.     div span:nth-child(3) {
  26.       align-self: flex-end;
  27.     }
  28.   </style>
  29. </head>
  31. <body>
  32.   <div>
  33.     <span>1</span>
  34.     <span>1</span>
  35.     <span>1</span>
  36.   </div>
  37. </body>
  39. </html>

image.png