JSFiddle - React, Tailwind, and code Playground

HTML

<div class="a">
    
    <div class="b">
      <div class="box"></div>
    </div>
    <div class="c">
      <div class="box"></div>
    </div>
    
  </div>

CSS

.box { background: red; height: 200px; width: 200px; margin: 15px; }
    .a { height: 500px; width: 500px; background: blue; }
    
    .b, .c { max-height: 0; overflow: hidden; transition: max-height 1s; transition-delay: 0; }

JavaScript

setTimeout(function () {
  $(".b").css("max-height", "500px");
  $(".c").css("max-height", "500px");
}, 500);


setTimeout(function () {
  $(".b").css("max-height", "0");  
}, 2000);