Roosevelt had the radio. Kennedy had television. Barack Obama, as it turned out, had memes.

The four years that Obama has served in the White House coincided with an explosion in Internet memes — Photoshopped images that are passed around via email, blogs, Twitter and Facebook and popularized on sites such as Reddit and Tumblr.

Though they're usually playful, memes can tell us a lot about what people really think about the president. They've tracked the hopes projected on him, the difficulties he's faced in office and the fears of his opponents. And though they are generated and sustained by grassroots Internet users, Obama has played a key role in popularizing many of them.

Here's a history of the first meme president, as told through seven major memes: the hope poster, Superman, the teleprompter, Spock, the Joker, the Jedi knight and "not bad."

It started with the Obama Hope Poster.

Then came Obama Superman.

And so on. And so on. And so on. Not bad.