Levels of Organization in the Human Body

The human body is organized in levels that build from simple parts to a complete living being. These levels increase in complexity from subatomic particles, atoms, and molecules to organelles, cells, tissues, organs, organ systems, and the organism.

At the chemical level, scientists study the sma...

Human body structures can be organized into hierarchical levels.

The chemical level is the most basic, where atoms combine to form molecules, such as proteins, lipids, and carbohydrates. Complex molecules further combine to form cells and organelles—specialized intracellular structures.

Cells are the smallest living unit of the hum...