http://repub.eur.nl/res/aut/59643/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/37501/ 2012-10-26T00:00:00Z Every human life starts with the fusion of an egg cell and a sperm cell, whereby the DNA content of both is combined into one cell and the blueprint of the human body is established. The DNA of this cell contains all information necessary to form a complete organism. During the development of the embryo, every newly formed cell will either continue to divide thereby contributing to expansion, or will specialize to form certain tissues or to carry out particular functions. The latter process is termed differentiation and underlies the development of all different cell types and tissue types present in the body. Together, the cells in a multicellular organism collaborate to support the germ cells: the cells that will form eggs or sperm to generate a next generation being the ultimate goal. In principle, a human body is a system consisting of many (1014, or one hundred thousand billion) cells that are grouped in specialized tissues and organs. Still, each somatic cell contains the complete DNA package, which is replicated during every cell cycle and is passed on to both daughter cells at cell division. Cell division is central to renewal of cell types with a limited life span such as blood and skin cells. It is estimated that 200 billion (109) new cells are generated in a human body every day, which equals approximately 2,500,000 new cells per second.