If you enjoy an egg for breakfast in the morning, when you are eating the yolk, you are eating a large single cell. What does that mean? What is a cell and what is it made of? What are the building blocks of life? The answer to these questions depends on the scale at which you are looking. In short, living things are made up of one or many cells, cells are made up of many different kinds of molecules, and molecules are made of atoms. In this chapter you will read about these basic ingredients of life. We will start with the smallest ingredients (atoms and elements), then examine the combination of atoms into molecules, and then explore cells, which are made up of molecules arranged in a highly organized fashion.