JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<div class="everything">
    <div class="menu">
        <div class="d1 active" data-content="home"></div>
        <div class="d2" data-content="about"></div>
        <div class="d3" data-content="contact"></div>
    </div>
    <div class="main">
        <div class="home">This is some example content.</div>
        <div class="about">This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
            <br>This is just some sample text that's being used to demonstrate animating the height when content changes.
   ...

CSS

body {
    background: -webkit-gradient(linear, left top, right bottom, from(rgba(237, 182, 165, 1)), to(rgba(126, 86, 112, 1)), color-stop(.7, #cc8e85));
    background: -moz-linear-gradient(rgba(237, 182, 165, 1) 0%, rgba(126, 86, 112, 1) 100%);
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: 0;
}
.everything {
    position: absolute;
    left: 0px;
    top: 0px;
    width: 102%;
    height: 100%;
    background: url(images/transparent_noise.png);
    overflow-y: scroll;
    z-index: 1;
}
.menu {
    position: relative;
    left: 0;
    right: 0;
    margin: auto;
    top: 50px;
    width: 308px;
    height: 50px;
    z-index: 999;
}
.d1, .d2, .d3 {
    position: relative;
    width: 100px;
    height: 50px;
    background-color: white;
    margin-bottom: 5px;
    opacity: .5;
    display: inline-block;
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    transition: all 0.5s ease;
}
.d1:hover, .d2:hover, .d3:hover {
    opacity: 1;
}
.active {
    opacity: 1;
}
.main {
    position: relative;
    left: 0;
    right: 0;
    margin: auto;
    top: 100px;
    width: 900px;
    height: 0;
    background-color: white;
    box-shadow: 0px 0px 1px gray;
    z-index: 2;
}
.home {
    position: relative;
    left: 0px;
    top: 0px;
    width: 900px;
    overflow: visible;
    z-index: 3;
    display: none;
}
.about {
    position: relative;
    left: 0px;
    top: 0px;
    width: 900px;
    overflow: visible;
    z-index: 3;
    display: none;
}
.contact {
    position: relative;
    left: 0px;
    top: 0px;
    width: 900px;
    overflow: visible;
    z-index: 3;
    display: none;
}
.hide {
    display: none;
}
.footer {
    position: relative;
    left: 0;
    right: 0;
    margin: auto;
    top: 110px;
    width: 900px;
    height: 50px;
    border: 1px dashed green;
    z-index: 999;
}

JavaScript

$(document).ready(function () {
    // removed height: 0 from children in stylesheet, set to display: none instead
    // set height to 0 on .main instead

    // click handler for menu items
    $('.menu > div').click(function () {
        $('.menu > div').removeClass('active');
        $(this).addClass('active');

        // get content associated w/ this menu item
        // the class is in data-content attribute of the menu item
        var contentDiv = $('.main').find('.' + $(this).data('content'));
        var contentHeight = contentDiv.height();

        if (!contentDiv.is(':visible')) {
            $('.main > div:visible').stop().fadeOut('slow', function () {
                $('.main').stop().delay(500).animate({
                    height: contentHeight + 'px'
                }, 500, function () {
                    contentDiv.stop().fadeIn('slow');
                });
            });
        }
    });

    // init home
    $(".main").height($('.main > .home').height());
    $('.home').show();
});