Greenville, North Carolina - Jimmy "MrBeast" Donaldson may be the world's biggest YouTube star, but he still has fears like the rest of us.

What is MrBeast afraid of? The answer may surprise you.

In his latest collaboration video, MrBeast teamed up with fellow YouTube star Mark Rober to conquer something he's been afraid of his entire life: his fear of heights.

Rober brought the iconic influencer to his secret "CrunchLabs" lair, and introduced him to an eight-foot drop called the "Fireman's Piston."

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The drop was assisted with a rope that used the pumping of two large pistons to slow the descent of any weight tied onto it.

After Rober explained the science behind it, and pointed out that children as young as five years old have made the leap, MrBeast reluctantly agreed to give it a go.

The star, who is famous for his wild stunts and challenges, including having himself buried alive for 50 hours, was absolutely terrified as he pushed himself several times to jump.

He finally conquered his fear, and jumped, but quickly declared he's "never doing that again."

As is pretty much the case with all of his projects, the clip has already garnered over 21 million views and counting.

Some fans have been laughing at the star's fear in the comments section, while others praise MrBeast for being "wholesome."