Interchangeable parts is a basic concept of creating identical or nearly identical parts to be mass produced. These parts can then be put together to form a product. For example, cars, computers, furniture, almost all products used today, are made from interchangeable parts. These parts are made with precision machines so each part can fit in any product that uses this part. Since it is no longer necessary to make each part one at a time and by hand, assembling products takes fewer workers. This lowers the cost of the product. Interchangeability of parts also allows products to be repaired by replacing a broken part with an identical new part. Eli Whitney was the first to use interchangeable parts in manufacturing.