Which area of hair is transplanted in a hair transplant?

Thanks to recent events, related to hair loss and hair transplantation.

As I read many posts, I started to become curious.

Since prevention is important for hair loss, prevention is emphasized, but for hair loss that has already progressed significantly, hair transplantation or...

Wigs are the only answer... I understand wigs, but...

Where do they take the hair from and transplant it during a hair transplant?

For people who have already experienced significant hair loss, their hair is

There isn't much... I'm curious about how they remove and transplant it, so I wanted to ask^^