Bill details the key engineering principles underlying plastic injection molding. He describes its history and, then, reveals the intricate details of the process. He shows viewers where to found, on any injection-molding product, the markings created by injection molding. He closes with a description of the one of the finest examples of the injection molding: the Lego brick. Overview video: https://www.youtube.com/watch?v=eUthHS3MTdA Mold manufacture: https://www.youtube.com/watch?v=seZqq1qxW30 Plastic bottle cap production: https://www.youtube.com/watch?v=WHwTHarf8Ck Making Lego bricks: https://www.youtube.com/watch?v=wnRRDIFNxoM 99 Percent Invisible: http://99percentinvisible.org/episode/the-post-billiards-age/