All living things have at least one cell. Cells are the basic building blocks of life. Unicellular organisms consist of one cell, and multicellular organisms contain more than one cell.
All living things share seven characteristics. The foundational characteristic is that all living things are composed of cells. In addition, all living things show organization in their structure, use energy, respond to the environment, grow, reproduce and adapt. Simple unicellular organisms consist of a single cell that carries out all the tasks required for life. More complex multicellular organisms contain different types of cells for different tasks. The cells are organized into tissues and organs that work together to meet the needs of the organism.