From the brains behind brains on, this is the Moment of Um.

Moment of Um comes to you from APM Studios. I'm smashed Dandy Boot.

Um. Um. from APM Studios. I'm Smash Dandy Boot.

I've been a movie stunt double for almost 10 years. That means I've jumped out of planes, slid downstairs, and crashed out windows. I've always tried to be as safe as possible,

but over the years I've collected a few injuries. The scars those ouches

leave behind are ways to remember and improve my stunt techniques. Here, see the scar on my shoulder?

I got this one driving a motor scooter into a cactus patch for Desert Desperado. And this one

here over my eyebrow? That one was from walking into a tree branch on the set of

mega space monkeys. It wasn't a stunt. I was just walking to our outdoor set and I didn't look

where I was going. And this one? Here on the left side of my butt? Ooh, well, that one's from a

bonfire scene in beach blazers that I'd prefer not to discuss in detail.

Anyway, my collection of scars is like a diary of all my stunts.

But that makes me wonder, why do I still have all my scars?

Why don't they heal and go away?

My buddy Noah wanted to know about this too.

So let's see what an expert has to say.

Hi, my name is Dr. Liz Farhad, and I'm a dermatologist.

And that means that I'm a doctor who specializes in skin.

If you get a small paper cut, your body will heal the area over

without scarring. But if you get a larger injury or have surgery, the deeper layers of the skin

are actually damaged. So the body has to send tissue to repair the skin over. The first step in repairing the area is a material called

fibrin, which forms a scaffolding. And there's cells in the skin called fibroblasts that work

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