The study of extracellular vesicles (EVs) has the potential to identify unknown cellular and molecular mechanisms that play important roles in intercellular communication as well as organ homeostasis and disease. Exosomes are a type of EV with an average diameter of about 100 nanometers. The biogenesis of exosomes involves their origin within the endosome and subsequent interactions with other intracellular vesicles and organelles to produce the final contents of the exosome. Their various components include nucleic acids, proteins, lipids, amino acids, and metabolites that reflect the cells of their origin. In various diseases, exosomes provide new insights into changes in cellular or tissue status, and their detection in biological fluids may provide multicomponent diagnostic information. Exosome-based therapies can be designed based on the material information transfer ability of exosomes.