RecruitingMolecular, Cellular, and Genetic Characterization of Human Adipose Tissue and Its Role in MetabolismBackground: The body uses energy from calories for basic functions like breathing and digesting food. Over time, when a person eats more calories than they burn, they may become overweight or obese. Obesity is a major health concern. Researchers want to look at fat and muscle tissue to learn more about metabolism. That is how the body uses food and other nutrients for normal function and energy. This research may help to develop new treatments for obesity and related diseases. Objective: To learn more about the role of fat and muscle in metabolism, particularly how fat and muscle store and use energy. Eligibility: Adults 18 years and older who have a planned surgery at NIH in which tissue can be collected by the surgeon. Design: Participants will be screened by their regular NIH doctor. Then researchers will contact them about this study. Participants will not have to make extra visits to NIH for this study. Researchers will collect samples during the participant s surgery. These will be fat tissue and skeletal muscle tissue. Muscle tissue will only be taken from tissue that is going to be discarded. Collecting the tissue will not add any time or any extra incisions than what is required for the surgery. After surgery, blood will be drawn. Some participants will have this done in the pre-op or post-op room. Others will have this done during their hospital stay.