President Barack Obama has been in the Oval Office for about two and a half years, but the world's most stressful job has taken its toll. Obama turns 50 on Thursday, reminding us that he remains one of our youngest presidents -- only Theodore Roosevelt and John F. Kennedy were younger when they took office -- but he no longer radiates the youthful vigor that helped make him such a sensation in 2008. The endless grind of the presidency, particularly given the ceaseless attacks he has endured from a Republican party determined to make him a one term president, have deepened some wrinkles and led some grey hairs to sprout.

When you were sworn in, you looked like the guy from the Old Spice commercials. Now you look like Louis Gossett Sr," comedian Seth Meyers joked at the White House Correspondents' dinner. "If your hair gets any whiter, the Tea Party is going to endorse it," he added.

Take a look at photos of Obama's journey, from 2004 to present: