How to insert an element as a first child inside other element in jquery

Question

I have Div that it contains some other elements like <p> , <ul> ,... How I can Add a Div as first child od my main div?

consider this tags:

<div id="MainDiv">
    <p>....
    <ul>...
    <span>....
</div>

I want it become:

<div id="MainDiv">
    <div id="newDiv"></div>
    <p>....
    <ul>...
    <span>....
</div>

Answer 1

$('#MainDiv').prepend('<div id="newDiv"></div>');