The human body is composed of approximately 200 distinctly different types of cells. These cells are organized into four basic tissues that, in turn, are assembled to form organs. When you examine tissue at a microscopic level, having the ability to detect the presence and location of the four basic tissues enables you to identify the organ that you are looking at. A basic knowledge of the general characteristics and cellular composition of these tissues is essential in histology, which is the study of tissues at the microscopic level.
Tissues are groups of similar cells performing a common function. There are four categories of tissues: