Tissue is a group of cells that have similar structure and that function
together as a unit. In biology, tissue is a cellular organizational level
between cells and a complete organ. A tissue is an ensemble of similar cells
and their extracellular matrix from the same origin that together carry out a
specific function. Organs are then formed by the functional grouping together of
There are four main tissue types in the body: epithelial, connective, muscle,
and nervous. Each is designed for specific functions.