Stereolithography, also known as 3-D layering or 3-D printing, allows you to create solid, plastic, three-dimensional (3-D) objects from CAD drawings in a matter of hours. Whether you are a mechanical engineer wanting to verify the fit of a part or an inventor looking to create a plastic prototype of an invention, stereolithography gives you a fast, easy way to turn CAD drawings into real objects. 3-D printing is a very good example of the age we live in. In the past, it could conceivably take months to prototype a part -- today you can do it hours. If you can dream up a product, you can hold a working model in your hands two days later! In this edition of How Stuff Works, we will take a tour of the stereolithography service bureau at PT CAM (Piedmont Triad Center for Advanced Manufacturing) so that you can understand everything involved and see some actual 3-D models that this technology has produced!