JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.1.1/js/bootstrap.min.js"></script>
<body>
    <div class="react-grid-Viewport">
        <div class="react-grid-Canvas opaque">
            <div class="rows">
                <div class="react-grid-Row">
                    <div class="react-grid-Cell">
                        <div class="react-grid-Cell__Value">
                            <div>
                                <div class="popup">
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </div>        
    </div>
</body>

CSS

.react-grid-Viewport {
    height: 150px;
    width: 400px;
    background-color: blue;
    overflow: hidden;
    position: absolute;
    top: 35px;
}

.react-grid-Canvas {
    height: 149px;
    width: 399px;
    background-color: lightblue;
    overflow-y: scroll;
    overflow-x: auto;
    position: absolute;
}

.rows {
    height: 100px;
    width: 700px;
    background-color: red;
    overflow: hidden;
}

.react-grid-Row {
    background-color: darkred;
    height: 35px;
    overflow: hidden;
}

.react-grid-Cell {
    background-color: green;
    position: absolute;
    left: 100px;
    width: 100px;
    height: 35px;
    overflow: visible;
}

.popup {
    background-color: lightgreen;
    opacity: 0.8;
    position: relative;
    width: 150px;
    height: 200px;
}