What do you see when you look at this picture? Is it just a mass of tangled ribbons? Look closely. It’s actually a complex pattern of three-dimensional shapes. It represents the structure of a common chemical found inside living cells. The chemical is a protein called hemoglobin. It is the protein in red blood cells which transports oxygen around the body. What are proteins? What other chemicals are found in living things? You will learn the answers to these questions as you read about the chemistry of life.