And now Nicholas is getting ready to walk over the 2000 degree Lake of Lava, one of his most dangerous feats yet.

Well, Reeve is on the scene.

Good morning.

Well, hey, good morning, George.

Nik Wallenda is nervous, and it's understandable if you'll take a look.

This walk of the Masaya volcano over these whipping winds through the toxic gases above that boiling lava.

It's all uncharted territory.

I spent the day with nickel and a learning about his process and his preparation.

The stakes are high, almost 1000 feet high.

The reality is I'm risking my life.

Tomorrow night, Aerialist Nik Wallenda will attempt his most daring feat yet, walking over one of the most volatile and dangerous volcanoes in the world.

The Messiah.

When you're at the middle and you look down, will you look down?

I absolutely will gets more about this beautiful environment in this beautiful piece of nature.

Located in the heart of Nicaragua, the Messiah is one of the world's most active volcanoes, and this 1800 foot long wire just over one inch thick, will be the only thing between him and the lava lake below, boiling it over 2000 degrees Fahrenheit the last week.

In the middle of the night, I'll wake up in cold sweats because of this walk.

Every step is dangerous.

Messiahs.

Plume of toxic gas is an unpredictable threat for, well, Linda, he'll be walking straight through it.

I'll be wearing goggles.

And what if they fog up?

What if What if they're not a fixed right?

My eyes start burning, and I can't see feats like this or his family legacy.

1/7 generation wire walker from the famed Flying Wallendas, the 41 year old has walked over the Grand Canyon and Niagara Falls and just eight months ago in Times Square.

But the walk across the Messiah will be the highest and longest walk well Linda has ever attempted on a cable he hadn't seen before.

I've never until this morning walked on the cable this diameter.

Our cameras were there as he took his first practice steps on that rusted wire Wednesday night.

Right about here.

This is where it will all begin.

What will go through your mind as you take these steps up, there will be everything from nerves to excitement, a little bit of fear, a lot of respect.

It's a dream.

Well, Linda told me that the element that most concerns him is the wind, because, as he says, it doesn't tell you how fast it's going.

It's so unpredictable here at the Masaya Volcano, the mouth of hell down there.

Those winds can come out of nowhere with no warning whipping up those toxic gases.

So there's a lot for Nick will lend it to contend with Georgie Boy.

There sure is, and we can't even wash that gulf right there.

But what surprised you most about his state of mind as he's heading into this?

Well, I stood with him, George at this wooden pyramid that he's going to be climbing up as he begins his 1800 foot walk across the crater and his honesty about the fear that he will be feeling in that moment and that he's been feeling leading up to this waking up in those cold sweats.

He told me that he's going to be very scared, but all he can do is literally put one foot in front of the other.

He says he has to do.

That's George.

It's almost reassuring to know that he's gonna be scared, but I think I should be.

But it's an amazing, amazing thanks very much.

You can see Nick walk over the Messiah Volcano Live tomorrow night at eight.

Eastern right here on ABC.

Hi, everyone.

George Stephanopoulos here.

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