In reference to anatomy, the smallest level of organizational classification used when studying the structure of a living organism.

The tissue level deals with the function and structure of tissues as a whole and their relationship to the body of the organism they make up.

Due to the complexity of a living organism, it may be studied on one or more of several structural levels. These levels are as follows, starting from smallest (micro) to largest (macro).

1. Chemical Level
2. Organelle-Level
3. Cellular Level
4. Tissue Level
5. Organ Level
6. Organ System Level
7. Organism Level