Expand / Collapse animated by JavaScript + CSS

Example HTML:

<div toggle-id="zero">Reveal Zero</div>

<p id="zero">I am Zero</p>

Reveal One

I am One
I am One
I am One
I am One
I am One

Reveal Two

I am Two
I am Two
I am Two
I am Two
I am Two
I am Two

Reveal Three

I am Three
I am Three
I am Three

Reveal Four

I am Four
I am Four
I am Four
I am Four
I am Four
I am Four
I am Four

Reveal Five

I am Five

Reveal Six

I am Six
I am Six
I am Six

Reveal Seven

I am Seven
I am Seven