We just learned about the Bone Marrow.
The bone marrow that makes blood cells is part of Haematopoiesis which comes from the Greek words αἷμα (aima) "blood" and ποιεῖν (poieín) "to make", so it means "to make blood".
A normal human body can make from one hundred billion to a trillion blood cells every day!
(from: wikipedia - haematopoiesis)
Kid Facts - Blast from the past: Retina
