We sing about it, we write about it, we just plain desire it.

Some even think we can find it by watching TV. Next to the meaning of life, we most want to know how to be happy.

Tonight at 10 (!) on UNC-TV, PBS begins a three-part documentary exploring happiness called "This Emotional Life."

(Each episode is two hours long, so you might want to set the DVR.)

Hosted by Harvard professor Daniel Gilbert, the documentary examines why happiness is so elusive, using a mix of science and personal stories.

We learn the brain science behind different facets of happiness.

Timing chips, donut sandwiches, beer runs and more.

Sorry folks, if you haven't already signed up for Saturday's Krispy Kreme Challenge, the race is all full. As of this morning, the cap of 5,000 runner-eaters had been reached. In fact, the race has overindulged slightly: 5,038 folks are registered. (Meaning if all 5,038 competitors were to eat a dozen, that would be 60,456 donuts down the hatch.)

If you hope to go out in a glaze of glory at Saturday's Krispy Kreme Challenge and have yet to register, you best act soon. For one, tomorrow is the last day you can register (go here). Perhaps of greater concern, registration is capped at 5,000 for this year's race and as of 4:03 this afternoon, 4,489 of those spots were taken.

To recap: run two miles from the N.C. State Belltower to the Krispy Kreme on Peace Street, eat a dozen donuts, run back the two miles to the Belltower. In 60 minutes or less. With all 12 donuts still on board. Do it and you will live in infamy (and your gastronomic tract in inflamy). (Note: If you don't think you're capable of eating a full dozen, you can sign up for the "Casual" category: Run 4 miles, eat "some" donuts." You get a T-shirt either way.)

The race is Saturday at 9:30 a.m.

From oven to tummy: Do you have the right stuff to eat a dozen donuts and run four miles?