The most important part of a wristwatch is its movement (but you already knew that, right?) Without this little mechanism ticking inside the case, the watch would be just a pretty but useless adornment around your wrist.

Watch movement is the mechanism that measures the passage of time and, in some models, also displays the current date. Movements may be entirely mechanical, electronic or a blend of the two. Most watches today have automatic movements, which means the motion of the wrist and body cause the rotor (a metal weight attached to a winding mechanism) to pivot.

Here's a bit of trivia for you: The modern rotor system was developed and patented by Rolex and introduced as the Oyster Perpetual in 1931.

However, the person who first developed a rotor was Abraham-Louis Perrelet (1729-1826), one of Switzerland's greatest watchmakers of all time, considered the father of the automatic watch. He introduced the concept in 1770 and was way ahead of his time since the invention was better suited to wristwatches and Perrelet lived in the pocket watch era. Obviously, the watches couldn't move in pockets enough to wind the mainspring, so the rotor system didn't perform well. Another Swiss watchmaker, Abraham-Louis Breguet (1747-1823) improved self-winding watches and named them "perpetuelles" (the likely source of Rolex's term). Other watchmaking greats of the 19th century advanced the concept. But it wasn't until World War I that Rolex perfected its system and automatic watches became popular.

Rolex's timepieces are either self- or manually-winding. There are also a few ladies' models powered by a quartz movement.

The self-winding model is by far the most common one. It is simply a mechanical watch with a mainspring wound by the motion of the wearer's arm. All the models in Rolex's Oyster Professional and Oyster Perpetual line - Explorer, GMT Master II, Submariner, Sea-Dweller, Cosmograph Daytona, Yacht-Master, Air-King, Datejust, and Day-Date are self-winding.

The gents' watches and a couple of women's models in the Cellini line are hand-wound. Since the Cellini collection is the simplest - in terms of design and function - of all the Rolex watches, the hand winding befits this classical image.

On the other hand (this just came naturally, I didn't intend the pun), most of the ladies' models in the Cellini collection are powered by a quartz movement. I admit that I see an obvious paradox and somewhat of an incoherence in having a classically simple timepiece with a quartz movement, which is usually associated with cheaper watches or fakes. Still, we can be quite certain that Rolex does not manufacture lesser-quality watches, so if for some reason you fancy having a quartz-powered timepiece, you can be sure it will keep on ticking with accuracy and precision for many years to come.