It is common knowledge that we need proteins, fats, carbohydrates, vitamins, and minerals in our diet. We are also aware that too much saturated fat and cholesterol puts us at risk for heart disease. Yet many of us have only a vague concept of what these molecules are, much less how they function in the human body. Study of the molecules that compose living organisms is called biochemistry. It overlaps with organic chemistry, the study of carbon-containing (organic) compounds, because the most distinctive biomolecules are organic compounds. In this chapter, we begin our discussion with some inorganic components of the body and progress to the organic ones. This will lay a foundation for understanding human form and function at many points later in the book.