Text prefixed with one to six pound signs (hash symbols, #) becomes a header <h1> through <h6>, according to how many pound signs were used.

# This is a first-level (`<h1>`) header
## This is a second-level (`<h2>`) header
### And so on.

This is a first-level (<h1>) header

This is a second-level (<h2>) header

And so on.

Atx-style headers may be optionally closed by adding trailing pound signs, which are ignored.

### This is a header with some trailing hashes ###

This is a header with some trailing hashes

At present Stack Exchange's flavor of markdown only seems to support up to three header levels (###), though Markdown supports all the way up to 6.

To create a first-level (<h1>) header, use the equal sign (=) in a line under your text:

All About Dogs
==============

All About Dogs

Use hyphens (-) for second-level (<h2>) headers:

The Debut Novel
---------------

The Debut Novel

The line below the header can be of any length.

Another header
--

Another header
-

Another header

Another header