JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.microsoft.com/ajax/jquery.validate/1.7/jquery.validate.js"></script>
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<div id="SearchHere">
    <div>
        <div>
            <div></div>
        </div>
    </div>
    <div></div>
    <div>
        <div>
            <div>
                <div id="selectThis"> </div>
            </div>
        </div>
    </div>
    <div>
        <div></div>
    </div>
</div>

JavaScript

var levels = 0;
var deepest;

$('#SearchHere').find('*').each(function() {
    if( !this.firstChild || this.firstChild.nodeType !== 1 ) {
        var levelsFromThis = $(this).parentsUntil('#SearchHere').length;
        if(levelsFromThis > levels) {
            levels = levelsFromThis;
            deepest = this;
        }
    }
});

alert( deepest.id );