I'm standing on the rooftop of NYU Lengone Health, a hospital in Midtown, Manhattan, scanning

the sky over the East River for a helicopter.

It's New York City, so there are tons of helicopters, but I'm looking for a specific one.

Finally, I spot it.

A white helicopter with red and white blades, carrying some very precious cargo.

The blades were to a halt, and some people step out.

One man is carrying a big white box.

Inside the box, a pig kidney.

This is science quickly.

I'm Tony Lewis.

I run back into the hospital to watch the small team arrive through the elevator doors,

wheeling the box with the kidney on ice.

I follow them right up to the operating floor, and that's as far as I can go.

Only surgeons and nurses and a handful of observers are allowed into the operating room.

There's a risk of the pig organ carrying a virus that could infect people, and they are

scrubbed in with personal protective equipment on.

The surgical staff also had to undergo special blood testing before and after the surgery

to ensure that they stay infection-free.

So I make my way back to a small room with a live video feed of the operation.

I'm here to watch an organ transplant, but not just any transplant.

A pig kidney is being transplanted into a human.

This is known as a Xenotransplant.

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