Definition:
The cell is the smallest unit of life. The human body is made of trillions of cells and each has a single function. For example: A muscle cell only contracts and a nerve cell only transports an impulse.
Cells are usually clumped together with other cells that do the same function. Collections of the same cells are called tissues. Only a few cells are left to float around disconnected from their neighbors: blood cells, eggs and sperm.
