DORA: I know you love slime, Wendell. What's snot, Wendell?
WENDELL: You might ask: what's not?
DORA: Groan.
WENDELL: Sorry. Snot is beautiful human slime. It's mucus. M-u-u- u-u-cus! And mucus is so important that it's found all over nature. Inside your nose, it's a thick, sticky, wet pudding-like gunk that coats your skin and hairs. When bits of stuff get stuck in your nose hairs, it's the mucus or snot that surrounds the stuff and traps it.

DORA: What's the recipe for snot?
WENDELL: Oh--just water, salt and chemicals to make it thick and slimey.

DORA: Then what are boogers?
WENDELL: Boogers are dried-up snot and dirty nose debris. They can be small slimy lumps or big, dry, brown clumps. Either way, boogers are filled with the junk that's in the air you breathe.
DORA: What kind of junk?
WENDELL: Dust, pollen, germs, sand, fungi, smoke, small particles from outer space!
DORA: Outer space?
WENDELL: Yup. Tiny pieces of meteorites.
DORA: Cool! Who knew?
WENDELL: The good thing about your mucus is that it helps trap all this junk and keep it from getting close into your lungs!

DORA: Why do I sneeze?
WENDELL: Why, Dora, the boogers have to come out somehow, don't they? Sometimes things (like boogers or pollen or pepper) irritate the delicate spaces inside your nose. Without being aware of it, your brain instructs you to take a deep breath. Next thing you know air and yucky stuff are blasting out of your nose at immense speed.
DORA: Do coughs work the same way?
WENDELL: Coughing is virtually the same, except that your mouth is open and you're getting rid of phlegm, the yucky stuff in your breathing tube. Snot and boogers -- they are gross, yucky and germ-filled -- and very functional. It's good to get rid of them. Wash your hands, Dora.
DORA: Thanks for the lesson in sanitation, Wendell.
WENDELL: Anytime.