Production of products and services usually involves multiple stages. These stages operate at different times and different speeds resulting in an operation that is not smooth. Much time can be spent waiting for another stage. By focusing on the flow of the product (or customer) through the process, each of the stages can be brought into harmony. Some of the changes that can be developed from this concept include the use of "just in time" inventory practices, the use of batching (blocking) to organize multiple activities, linking parallel activities during the process, and developing timing of events to match the predicted flow of the process.