At MIT we are taught to be innovative and inventive. We create novel engineering designs that will change the world. It can be challenging, though, to know when and how to prototype a concept in the early phases of development. But engineering designs will only have impact if they solve a real customer problem, and make it all the way through the product development process on to mass production, and into the hands of the customers with the need. In this talk, we will use two case studies to walk through the product development cycle from idea to prototype and manufacturing to obsolescence, including customer development and lean startup techniques to increase your chances for success.