<!DOCTYPE html>
<html>
<head>
<style>
.descendants * {
display: block;
border: 2px solid lightgrey;
color: lightgrey;
padding: 5px;
margin: 15px;
}
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("div").children("p.first").css({"color": "red", "border": "2px solid red"});
});
</script>
</head>
<body>
<div class="descendants" style="width:500px;">div (current element)
<p class="first">p (child)
<span>span (grandchild)</span>
</p>
<p class="second">p (child)
<span>span (grandchild)</span>
</p>
</div>
</body>
</html>