Leonardo da Vinci studied a ball bearing using rolling balls between surfaces. His sketches show how rolling elements could reduce friction when one part moved against another.
Leonardo explored the idea around 1498 while working on mechanical systems. A bearing separates moving surfaces and supports a load, while balls or other rolling elements replace much of the sliding friction with rolling friction. This principle is central to many modern machines.
Leonardo is often credited with an early recorded design, but he did not invent every form of bearing. Ancient and medieval machines used other low-friction arrangements, including rollers and plain bearings. Modern ball bearings use carefully manufactured rings, balls, cages, and lubrication; Leonardo's drawing was an important conceptual step rather than a mass-produced industrial component.