MrsFtG has one of these Borel Kaleidoscope cocktail watches with a clear back. You get to see how it ticks without taking the back off. It’s really cool.
(Of course I took the back off a few years ago to get it running well again, but no harm, and a lot of good, done.)
It is amazing but then they were basically the smart phone of their day; a technology being continually improved by the best engineers over many iterations.
Moreover they were a technology (no pun intended) whose time had come. The demands of urban life including factory, trolley and train schedules created an enormous potential demand if someone could inexpensively produce reasonably accurate watches. So iterative improvements in quality and price took off.
In one of the Sherlock Holmes stories, when Holmes first meets Watson, he deduces a great many things about him just by a glance at Watson’s pocket watch. In one of the modern adaptations, they used that scene nearly verbatim, just with the watch replaced by a phone.
In the Red Headed League, when they go into the bank vault at night, Homes asks Watson to bring his “repeater”. Which is a pretty remarkable device. A watch that tells the time by chiming on request. As they are waiting in total darkness for the villains of the story to arrive, this makes sense.
Watson’s repeater would have been a pocket watch, so not as great marvel of horology as a wristwatch repeater, but about as sophisticated a device as was possible.
In the modern world of ultra expensive watch collecting, a repeater pretty much tops out the hierarchy of complications. H Moser does a repeater that eschews a face with hands. Probably the most coveted watch in modern times is the Phillipe Dufour Grande Sonnorie. Handmade. Yours in exchange for your first born child.
If you’re interested is seeing how watches work in detail, watch (har!) any of the videos by the amateur watchmaker at Wristwatch Revival. You may initially balk at a 50+ minute video of a guy taking a watch apart, fixing it, and putting it back together, but if you’re like me (and many of his other fans who say the same thing) you’ll find it fascinating and strangely compelling.
He’s extremely knowledgeable and explains what he’s doing and why in a clear and easy-to-understand way. And he has an amazing collection of highly specialized tools!
That was indeed a fascinating rabbit hole. The complexity of a “simple” clock is unbelievable!
Following up on Francis’s comment, see:
Learning that high-end watches have different frequencies came as a surprise to me. I don’t recall frequency being mentioned in advertising or on the box.
I wore wrist watches since childhood and probably never had anything but the off the shelf standard 5 ticks a second.
Now I wonder about the frequency of my $14 Timex. 
It was accurate enough when I was in high school. I didn’t get a Seiko until college.
Link A Guide to the Accurate, Mesmerizing High-Beat Watch | Gear Patrol
Tag Heuer produced a watch, or at least a prototype of one, where the chronograph portion of the movement runs at 1,000 hertz, or 2,000 ‘ticks’ per second. At that furious pace, the chronograph has a power reserve such that it can only run for about four minutes before winding.
The world’s fastest watches: movements with oscillating frequencies far beyond 4 Hz
In this thread, I speculated about building a Babbage Analytical Engine with watch-scale components. While impractical for a watch, a 1000 hz escapement would be great for such a computer.
For an amateur, Marshall is pretty good. His video making and editing skills and patter are really what make his videos very watchable.
*Note, i’m an amateur who is MUCH LESS good than Marshall 
Watchmaking/repair tools are crazy. I have a pretty good set, mostly vintage (better quality than you can find today without spending $$$$). Collecting tools becomes as much of a thing as the watches themselves. Its a common thing (at least for me) to need a $70 tool to fix a $20 pocket watch, then never need to use the tool again …
Marshall’s videos are very entertaining and kept me occupied while my wife was doing chemo last year. But once you’ve watched a bunch of them, a little variety is nice. There are a number of really good watch repair channels, but my current favorite is @RedDeadRestoration. He doesn’t talk, so you only hear the sound of the parts, tools and machines.
Once you’ve seen enough narrated videos, it’s kind of fun to imagine your own voice over. I’ll never see someone using a mainspring winder to insert the spring into the barrel without hearing Marshall’s voice exclaiming that that’s his favorite step.