3D printing, or additive manufacturing, is the process of making three-dimensional solid objects from a digital file. This contrasts to subtractive processes, such as the NC machining of traditional manufacturing, in which material is removed rather than being added.

An object is made in an additive manner by depositing successive layers of material until the entire object is built. Each layer can be visualized as a thinly sliced horizontal cross-section of the eventual object.

It all starts with a digital or virtual design of the object you want to create, made with a 3D modeling program or by using a 3D scanner to copy an existing, usually hand-sculpted object. The 3D scanner makes a 3D digital copy of the object that is used as the template for 3D printing.

From prosthetics to teeth to heart valves, the tech brings custom designs into operating rooms and doctors’ offices. Hospitals and researchers are experimenting with 3D printers in hopes of printing human tissue and organs.