Processing one item at a time through the entire production sequence, rather than processing a batch at each station before moving the batch forward. One-piece flow minimizes work-in-progress inventory, makes defects immediately visible (the next station catches the problem within seconds, not hours), and dramatically reduces lead time. taiichi-ohno's early experiments with multi-machine operation were the genesis of one-piece flow — a single worker operating multiple machines in sequence rather than a batch operator at a single machine. One-piece flow requires balanced workstations (takt-time), reliable processes (jidoka), fast changeover (smed), and small lot sizes. It is the manufacturing embodiment of "small batches" that appears in every lean methodology downstream — from continuous integration in software to the minimum viable product in Lean Startup.