Investors in additive manufacturing companies 3D Systems (DDD -4.52%) and Stratasys (SSYS -0.91%) have seen phenomenal share-price run-ups over the past year, and if today's nearly 10% pullbacks are any indication, upcoming earnings could be quite dramatic. In the following video, Motley Fool analysts Blake Bos and Isaac Pino discuss how investors should approach investing in this hot sector today and highlight one 3-D printing company set to go public soon -- ExOne.