Hey, it's Floral Lichtenen, and you're listening to Science Friday.

On today's episode, the science of replacing body parts from hearts to hair.

If you take armpit hair and put it on the head, this is a quote from some clinic in L.A.

It is difficult to style.

It seems like every week there is a new headline about some kind of sci-fi-sounding organ transplant.

Eyeballs, 3D-printed kidneys, pig hearts. In the new book, Replaceable You, Adventures in Human

Anatomy, science writer Mary Roach

chronicles this effort to fabricate human body parts and why it can be so monumentally difficult.

The book does not skimp on the details, and neither do we. So if you want to hear the nitty-gritty

on hair transplants or vaginoplasties. Today is your day. And if you

don't, don't say we didn't warn you. Mary, welcome to Science Friday. Thank you, Flora.

This is your fifth book on the human body, I think, if I'm counting right. It's a characteristically

wild ride. What keeps you curious about our bodies? Well, they're just

endlessly amazing and weird, I think, is the answer. I mean, because I didn't study biology or

physiology in any formal way every time I step into a new system of the body, whether

it's the elementary canal, you know, the gut or sexual physiology or whatever it is, I'm just

kind of gobsmacked by the stuff that's kind of going on behind the scenes, behind the curtain.

It's kind of miraculous and weird. Behind the skin drapes. Yeah.

Yeah. The skin drapes. Exactly. Mary, let's start with a transplant that weirdly is dominating my social

feeds right now. Hair transplants. What is the state of hair transplant science? Yeah, hair transplants are interesting. The principle by which they work is something called donor dominance. So if you take follicles from the sides or the back of the head where they're not sensitive to testosterone, they're not going to fall out, you put those on the top of the head. Now they're going to stay permanent. They're not going to fall out. You put those on the top of the head.

Now they're going to stay permanent. They're going to fall out because they retain the

characteristics of the back of the head, side and back of the head hair. They've got that back of the

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