Cell specialisation is the classification of cells according to special functions. The human body has an infinite number of cells which get replenished everyday. Examples of specialised cells include nerve cells, blood cells and epithelial cells.
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Specialized cell is one that has differentiated embryonic stem cells. They are undifferentiated meaning they have the ability to become any type of cell in the body. As development progresses and cells divides and different cells take on different functions and are thus said to be specialized.