Hand over hand, foot over foot, Chris Sharma takes on one of the most daunting challenges for a climber—a California redwood tree. He struggles to find his next foothold in the morning fog.

You may have climbed a tall tree before, but you have never climbed one like this. Until now, no one has. The tree Mr. Sharma climbs is 252 feet tall. Its trunk is 26 feet around. Mr. Sharma has been preparing for this climb for a year. And he’s known as one of the best rock climbers in the world!

In the climb, Mr. Sharma uses only his hands and feet. He grips the bark tightly. A rope and a harness protect him from falling. But they don’t hoist him up the tree at all.

Seven cameras from Mr. Sharma’s sponsor, Red Bull, capture the climb. Two thousand feet of rope hold the cameras at the correct angles. At least one camera hangs from a nearby tree.

Mr. Sharma lives in Spain. He moved there to climb rocks. But he grew up in California. Climbing the redwoods makes him feel like a kid again. Before he began, he wondered if climbing the tree was even possible. But he had to try.

Because redwoods are endangered, it is illegal to climb them. But Mr. Sharma got special permission. He isn’t just climbing. He’s doing scientific research. Some biologists asked him to collect data as he climbed. They hope the data will show how the redwoods are handling the California drought.

Few people make it all the way to a redwood forest’s canopy. Because of that, humans haven’t ever studied many of the plants and animals living high in treetops. Some of the species don’t even have names.

Finally, Mr. Sharma raises his body to the very top of the tree. He has made it into the canopy!