If there was no cellular specialization, every cell in your body would be the same
Why Does the Body Have to Specialize
Cell differentiation is how generic embryonic cells become specialized cells. This occurs through gene expression, this is what dictates how a cell functions.
Where are they found in?
Found in many multicellular organisms. Cells of the same type are usually organized into tissues that in turn form organs.
Purpose
Groups of specialized cells cooperate to form a tissue, such as a muscle. Different tissues are in turn grouped together to form larger functional units, called organs, and thus give form to the body