This document discusses the strengths and materials used for different 3D printing technologies, including powder-based systems that can print with plastics, metals and ceramics; multi-material printers that can print with metal wire, powder and ceramics; filament and pellet-based printers that allow printing in multiple colors with good structural properties using thermoplastics; full-color powder printers for plastics, metals, ceramics and glass; resin printers providing high accuracy and smooth surfaces for printing photopolymer resins; and sheet material printers providing high build rates at relatively low cost using paper, plastic sheets and metal tapes.