Kids in tests on Everest's slopes
How far would you go to help save lives? Well a group of kids from the UK have not only travelled halfway across the world, but even went halfway up the world's highest mountain!
It's all so they could take part in experiments which scientists reckon could save millions of lives in the future.
The Xtreme-Everest 2 expedition is hoping to find new treatments for sick people whose organs struggle due to low levels of oxygen in their blood.
It's the largest high-altitude research study of its kind ever undertaken, with more than 200 adults and children taking part.
Diseases of the lungs and heart can mean there is less oxygen available for the body's vital organs.
Some people cope with this but others don't and doctors aren't sure why.
To try and come up with answers, the Xtreme-Everest 2 expedition is taking groups of healthy kids and adults to the Himalayas, a mountain range in Asia, where there's less oxygen in the air due to the higher altitude.
They're undergoing all sorts of tests to see how their bodies cope with the conditions.
The experiments are a collaboration between Duke University in America, the University of Southampton and University College London.
Science presenter Greg Foot went along with one group of kids - check out his video report above.