JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header" style="width: 100%;">
			<div id="teste"></div>
			<div id="teste2"></div>
</div>

CSS

#teste2{
		width: 200px; 
		height: 100px; 
		background-color:black; 
		float:right; 
		margin-top: -100px;

	 }

	 #teste{
		width: 200px;
		 height: 100px; 
		 background-color: red;
		 display: flex; /* Safari */
   
	 }
	 
	 @media screen and (max-width: 600px) {
		 #teste,#teste2{
			 width:100%;
			 float:left;
		 }
		 #teste2 {
			 margin-top:0;
		 }
	 }