JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class='main-header'>
        <img src='http://imageserver.amlaw.com/publications/LAW-14-05656_header.jpg'>
    </div>
</body>

CSS

.main-header {
    background-color: red;
}

* {
    margin: 0;
    padding: 0;
    border: 0;
}

/* Uncomment something: */
    
.main-header {
    /* line-height: 0; */
}

img {
    /* display: block; */
    /* float: left; */
}