JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<div class="chat">
    <div class="head"></div>
    <div class="body">
        <table border="0" width="100%" cellpadding="0" cellspacing="0">
            <tbody>
                <tr>
                    <td align="left" width="40">
                        <img src="http://www.exclutips.com/wp-content/uploads/2015/08/wordpress-custom-user-avatar.png" style="
                            width: 32px;
                            height: 32px;
                            display: block;
                            border: 1px solid rgba(0, 0, 0, .1);
                            cursor: pointer;
                            ">
                    </td>

                    <td align="left" width="136">
                        <div class="user-name">User Name</div>
                    </td>

                    <td align="right">
                        <span class="online-icon"></span>
                    </td>
                </tr>
            </tbody>
        </table>
                <table border="0" width="100%" cellpadding="0" cellspacing="0">
            <tbody>
                <tr>
                    <td align="left" width="40">
                        <img src="http://www.exclutips.com/wp-content/uploads/2015/08/wordpress-custom-user-avatar.png" style="
                            width: 32px;
                            height: 32px;
                            display: block;
                            border: 1px solid rgba(0, 0, 0, .1);
                            cursor: pointer;
                            ">
                    </td>

                    <td align="left" width="136">
                        <div class="user-name">User Name</div>
                    </td>

                    <td align="right">
                        <span class="online-icon"></span>
                    </td>
                </tr>
            </tbody>
        </table>
            ...

CSS

* { 
    font-family: "Segoe UI"; 
    box-sizing:border-box;
    }

    html {
        font-size: 100%;
        -webkit-text-size-adjust: 100%;
        -ms-text-size-adjust: 100%;
        height: 100%;
    }

    body {
        margin: 0;
        padding: 0;
        background: #F2F2F2;
        height: 100%;
    }

    input, select {
        display: block;
        width: 100%;
        padding: 5px;
        outline: none;
        border-width: 1px;
        border-style: solid;
        border-radius: 0;
        background: #fff;
        font-size: 12px;
        color: #6B6B6B;
        appearance:normal;
        -moz-appearance:none;
        -webkit-appearance:none;
        border-color: #BDBDBD;
    }

    div, textarea, input, select, button, a { box-sizing: border-box; -moz-box-sizing: border-box; }

    .chat {
        /*display: table;*/
        border-left: 1px solid #ccc;
        position: fixed;
        height: 100%;
        top: 0;
        right: 0;
        bottom: 0;
        width: 200px;
        margin: 0;
        padding: 0;
        background: #E1E1E1;
    }
    .chat .head {
        height: 52px;
    }
    .chat .body {
        overflow-y: auto;
    }
    .chat .body table {
        cursor: pointer;
        padding: 5px;
    }
    .chat .body table .user-name {
        color: #333;
        font-size: 12px;
        overflow: hidden;
        white-space: nowrap;
        text-overflow: ellipsis;
        max-width: 136px;
    }
    .chat .body table .online-icon {
        background: rgb(66, 183, 42);
        border-radius: 50%;
        display: inline-block;
        height: 6px;
        margin-left: 4px;
        width: 6px;
    }
    .chat .body table:hover {
        background: #F2F2F2;
    }
    .chat .footer {
    }
    .chat .footer input {
        border-top: 1px solid #ccc;
        border-bottom: 0;
        border-right: 0;
        border-left: 0;
        padding: 6px 5px;
    }

JavaScript

$(document).ready(function () {
	setSize();
    $(window).on('resize',setSize);
});

function setSize(){
	var CH = $('.chat').height(),
    	HH = $('.chat .head').height(),
        FH = $('.chat .footer').height();
	$('.chat .body').height(CH-HH-FH);
}