NSES Content Standard C  Life Science: Structure and function in living systems Grades 5-8, page 156 All organisms are composed of cells--the fundamental unit of life. Most organisms are single cells; other organisms, including humans, are multicellular.

 
Benchmark 5C The Living Environment: Cells
Grades 3-5, page 111
Some living things consist of a single cell. Like familiar organisms, they need food, water, and air; a way to dispose of waste; and an environment they can live in.

Benchmark 5C The Living Environment: Cells
Grades 3-5, page 111
Microscopes make it possible to see that living things are made mostly of cells. Some organisms are made of a collection of similar cells that benefit from cooperating. Some organisms' cells vary greatly in appearance and perform very different roles in the organism.

Benchmark 5C The Living Environment: Cells
Grades 6-8, page 112
All living things are composed of cells, from just one to many millions, whose details usually are visible only through a microscope. Different body tissues and organs are made up of different kinds of cells. The cells in similar tissues and organs in other animals are similar to those in human beings but differ somewhat from cells found in plants.