This document discusses 3D printing technology for printing biological structures. It begins with an abstract that provides an overview of 3D printing as a process of prototyping where a structure is synthesized from a 3D model. The document then covers the core technology of 3D printing in the biological domain and its applications. It discusses how 3D printing is being applied in various medical situations and for developing medical research. The document also provides background on the history and development of 3D printing technology.