As anyone who's ever used a cotton swab knows, human ears generate a fair amount of earwax. But what exactly is the stuff, and do you need to make a point of clearing it out every so often?
WHAT'S INSIDE: HUMAN BODY
- Body Parts
- Body Systems
The heart is a vital organ that basically serves as a pump. Learn about heart chambers and valves, blood flow, the heart's electrical system and blood supply. Read more about how this amazing organ works.
During early pregnancy, both male and female human embryos develop something called milk lines, ridges that eventually recede into nipples. Why have some species lost this unisex trait, and can human men actually produce milk?