Biointegration is the process by which a non-biological material or device establishes a stable, functional, and often intimate interface with living biological tissues and systems. It investigates the complex reciprocal interactions occurring at this interface, focusing on minimizing adverse host responses such as inflammation, fibrosis, and immunological rejection, while promoting beneficial interactions like tissue ingrowth, vascularization, and long-term functional integration. Its significance lies in facilitating the successful development and application of biomedical implants, prosthetics, sensors, and tissue-engineered constructs crucial for therapeutic, diagnostic, and regenerative medicine.