JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.min.css">
<div class="wrapper">
<div id="left-menu">
    <div class="btn-group open">
        <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false">Action <span class="caret"></span>

        </button>
        <ul class="dropdown-menu" role="menu">
            <li><a href="#">Action</a>
            </li>
            <li><a href="#">Another action</a>
            </li>
            <li><a href="#">Something else here</a>
            </li>
            <li class="divider"></li>
            <li><a href="#">Separated link</a>
            </li>
        </ul>
    </div>
    <br />    <br />    <br />
    <p>Some menu items that can become super long in height</p>
    <p>Some menu items that can become super long in height</p>
    <p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p>
    <p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p><p>Some menu items that can become super long in height</p>
</div>
    </div>
<div...

CSS

#left-menu {
        position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    width: 200px;
    background: #f1f1f1;
    overflow:auto;
}
.btn-group {
    margin-left: 10px;
    margin-top: 30px;
}

#main-content{
    position: fixed;
    top: 0;
    bottom: 0;
    left: 150px;
    right: 0;
}