In the video below, Motley Fool industrials analyst Blake Bos takes a look at news that investors need to know about in the 3-D printing industry that's coming out of the Rapid Ready conference, a major event for the industry. Blake discusses comments made by Terry Wohlers at the conference about just how much the industry as a whole has grown over the past year, and what those growth numbers have been for some of the most prominent players in the space. He also talks about why the explosion in media coverage of 3-D printing has given the public the illusion that this was an industry that erupted overnight. Blake tells investors why they might need to be careful in this space; he discusses the price to sales ratios for 3D Systems (DDD 4.14%), Stratasys (SSYS -1.66%), and ExOne (XONE), and shows investors why these stocks look priced to perfection at the moment.