In the eighth title in the Mysterious You series, go with the flow and learn all about blood and the circulatory system. Topics include what blood's made from, how it moves around our body, the role of the heart, and how our organs clean our blood. Discover that over your lifetime your heart will beat roughly 2.5 billion times, that by the time you're an adult your blood vessels will be long enough to reach around the earth -- twice! and that only about 60 people in the whole world have the rare K zero blood type.