JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div id="menu" class="menu">
        MENU
    </div>
    <div class="resto">
        RESTO DO CONTEUDO
    </div>
</div>

CSS

.container {
    width: 100%;
    overflow: hidden;
}

.menu{width: 25%; float: left; position:blocked; background-color: blue}
.resto{background-color:#ccc; width: 75%; float: left;}