3D printing, also known as additive manufacturing, involves using printers to deposit layers of material to build 3D objects. This document discusses the history and current state of 3D printing, including its potential medical applications to print tissues, implants, and prosthetics. It also addresses some common concerns about 3D printing, such as liability issues if a library's 3D printer was used to print a gun. The document suggests that libraries can educate patrons about 3D printing and provide access to the technology for educational purposes.