JSFiddle - React, Tailwind, and code Playground

HTML

<div id="Header">  

</div>
<div id="Content">

</div>

CSS

html{
  height:100vh; 
}

body{
  height:100%;
  background-color:yellow;
  overflow:auto;
  margin:0;
/*   display: flex;
  flex-direction: column; */
}
#Header{
  height:3em;
 
}

#Content{  
  background-color:green; 
  height: 100%;
}