The amount of available oxygen at the highest place on Earth is just under 7%. Explorers risk their lives and test their lungs traveling to these great heights atop mountains. Who are these adventurers and why do they do it? Turn the pages to find out!

Did you know the deepest parts of the ocean are still largely unexplored? Courageous explorers risk their lives to go to these great ocean depths. Other explorers journey into deep volcanoes, caves and mines. Who are they and why are they seeking a glimpse of the world deep below the Earth's surface? Turn the pages to find out!