This document outlines topics from a lesson on 3D printing. It discusses what 3D printing is, how it works by building objects layer-by-layer, and examples of 3D printing. A brief history of 3D printing is provided, including the first 3D printing machine. Open-source 3D printing like RepRap and Makerbot are explained. The document also covers getting started with the 3D modeling software Tinkercad, including tutorials on basic functions like object manipulation and making holes.