Your Blood Vessels Could Circle Earth Four Times Laid end to end, an adult's blood vessels could circle Earth's equator four ...

Humans are complex organisms made up of trillions of cells, each with their own structure and function. Scientists have come a long way in estimating the number of cells in the average human body.

The body is, for all intents and purposes, an extraordinarily complex machine. This requires a multitude of parts all working together in complicated relationships from the micro- to macromolecular ...