Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object, co-developed between FDA and NSTA, is the second of four Science Objects in the Nutrition SciPack. It discusses how the body makes use of foods’ nutrients, after food is digested into simpler substances. These simpler substances must then be absorbed through the lining of the small intestine and transported for use throughout the body for physiological processes. In cells, these nutrients and substances derived from them are taken in and react to provide the biochemical constituents needed to synthesize other molecules. Some cells store energy from the breakdown of some nutrients in specific chemicals that are used to carry out the many functions of the cell. The circulatory system moves substances to the cells and removes waste products. Lungs take in oxygen for metabolism and eliminate the carbon dioxide produced, excretory systems rid the body of dissolved and solid waste products, and the skin and lungs rid the body of excess heat energy.