Before you even undertake the work to create a thing, there’s some assessment of whether it’s possible and how valuable it will be. (For some extremely nebulous definition of value — I’ll talk about that later). Some ideas take a large chunk of resources to assess (‘fat’ ideas). In other cases, a spreadsheet and well-founded assumptions can make a strong case that “it will be hard, but if we pull off all these things that don’t violate physics along this critical path, it will be incredible” (‘lean’ ideas).