Introduction :-

Human body is made up of several kind of cells. In multi cellular organisms, specialized cell types are formed by grouping of thousands of cell. The cells of one or more kinds are arranged together in a particular manner and co-operate to perform a specific function, this grouping of cell is called tissue.

Origin of tissue :- undifferentiated cells of primary germ layer (ectoderm, mesoderm and endoderm) in an embryo undergoes multiplication by mitosis and cell differentiation by inactivation of specific germs. This results in tissue formation.