Every individual living thing is made of smaller parts. The smaller parts have different functions, but all of the parts work together to enable the individual to live and survive in its environment. The cell is the basic building block of all living things.
Cells Alive Some tiny organisms , called protists , are made of only one cell.
Since the single cell must work alone, it has to do everything to make sure that the organism survives. Protists can not be seen with the human eye. To observe tiny organisms in their microworlds, you can use a microscope . Microworlds Extremophiles Multi-celled organisms are more complex. Different parts have different functions, each part sharing the work and cooperating to make sure that the organism survives.