In virtual top-10 of the most overlooked parts of the watch movement, the crown will very likely land somewhere at podium position. We use it almost every day, taking it for granted, but do you actually know how it is constructed and what has shaped its appearance during the last 150 years? 
One often sees the crown as a utilitarian item, unworthy of deep study or even a trivial curiosity. Just browsing through a catalogue of any brand, we learn a lot about the bezel, the sturdiness of sapphire case back or a shape of the arrows. However, the crown by means of which we’ll communicate with the watch, will be mentioned only if its set with precious stones, and then again, only in terms of the total carat weight. And let’s make it clear: the diversity of designs, placement and even functionality is huge. In addition to setting time and date, crown is used for winding, and in some chronographs even for starting the countdown. Above all — it is the main surface of the watch for direct owners interaction. Aesthetics here mostly intersects with functional needs, and no matter how exquisite the decoration is, its primarily purpose includes a comfortable grip for your fingers. 
Up to the nineteenth century the industry managed to exist without the crown. Pocket watches had a perfect round shape, and the winding was done via the key, which could easily be lost. The ports for it also had some obvious flaws like letting the dust and moisture inside. In 1820 British watchmaker John Roger Arnold, son of the famous inventor John Arnold, patented the first prototype of the crown, protecting the calibre from external influences. His teacher Abraham-Louis Breguet later modified the mechanism, making it suitable for smaller sized pieces. 
However, it was Jean-Adrien Philippe, a future partner in Patek Philippe, who started a revolution. In 1844, he presented a keyless mechanism with a two-stage system of the transfer shaft. Its wheel stayed in constant engagement with the ratchet, leading to the winding mechanism, and connected to the hour and minute wheels only in the time-setting mode. The simplicity and effectiveness of the design have changed the landscape of the industry forever. Philippe’s patent was awarded a gold medal at the Exposition Universelle in Paris, and later became an integrated part of almost any wristwatch, quartz watch, and now even smartwatch. 
The majority of modern watches features a crown at 3 o’clock, but it’s far from mandatory. Some brands place it at 12 o’clock following the pocket watch geometry, some designers prefer the locations of ‘1, 30’ or ‘4, 30’ and so on. In the decoration department each manufacture also has its own way. As a result some crowns act almost like an additional trademarks —think the reversed ‘P’ letters in Patek Philippes of the 1950s, a huge onion-crown on Longines of 30-50s, or gem-set Cartier crowns. And of course Well anyone would instantly recognize the Rolex crown with, you’ve guessed it, a crown logo. By the way, another crown-wise technological leap happened in 1926 thanks to Rolex: the legendary Oyster model has set new standards of water resistance. A screw-down crown guaranteeing complete movement isolation and soon became somewhat of a role model for modern divers.  
From time to time the most ambitious artisans still try to challenge the status quo. For example, a member of the Académie Horlogère des Créateurs Indépendants (AHCI) Marc Jenni entrusted the crown functions to the rotating bezel: there are three familiar modes — winding, time setting or date setting. 
There are some hybrid systems too, such as the Rebellion T-1000. A rectangular lever carries out the winding of its six barrels, but you still have to set the current time via traditional crown.