Secrets of the Human Body206 bones. One heart. Two eyes. Ten fingers. You may think you know what makes up a human. But it turns out our bodies are full of surprises. What makes tears of joy different from tears of sadness? Why is a gut feeling so much smarter than you think? And why is 90% of you not even human? You may think you know the human body heart, lungs, brain and bones but your body is full of extraordinary mysteries that science is only just beginning to