The human body is a complex machine. It is made up of trillions of cells and each one of these cells has its own life span. The cells have to be replaced every day and when they die, they are …

Multiple sites – one purpose
The human body is a complex machine. It is made up of trillions of cells and each one of these cells has its own life span. The cells have to be replaced every day and when they die, they are …