The pancreas is an inner organ composed of endocrine cells that are responsible for the secretion of polypeptide hormones, such as insulin, into the blood stream, and exocrine cells that are responsible for the secretion of digestive enzymes, such as trypsinogen or amylase, into the pancreatic ducts. Increasingly, the pancreas is being recognized as a central player regulating metabolic processes throughout the human body. Here, we describe some of the most essential features of this vital organ and its interactions with liver, muscle, and adipose tissue.