Look at your classmates. What are they made of?

Like all living organisms, humans consist of cells.

Cells are the building blocks of life. The cell's nucleus contains its genome, or hereditary information. The nucleus is surrounded by cytoplasm, which consists mainly of water. 

The cell can contain various organelles. Organelles are structures that fulfill various functions inside the cell. Some organelles can produce energy, whereas others can break down waste material. 

The cell is separated from its surroundings by a cell membrane.