The beginning for almost everything that is made.
"I need a prototype to see if it works the way I've planned it too."
Prototyping is the process of putting together a model that works in order to test for defects in design and get feedback. Prototyping is an integral part of the design stage. It is here where the cost benefit analysis is performed and realized. It is also at this stage where the product is refined for any usability or aesthetic reasons.