JSFiddle - React, Tailwind, and code Playground

HTML

<div class="un"><a href="#"><img src="http://www.strikingsupport.com/wp-content/uploads/2013/02/slide-01.jpg"></a></div>

CSS

.un
{
    width: 100%;
    height: auto
}
.un img
{
    max-width: 100%;
    height: auto:    
}