Over the course of time, multiple different kinds of clocks were made however, mechanical clocks would quickly prove their worth as being very reliable (for the time), and were the de facto timepiece until the development of the true pendulum clock in the late 17th Century by Christian Huygens. Galileo would show a little earlier, in 1581, that pendulums could be used to help keep clocks accurate so long as the pendulum was swinging.
The mainspring was invented in the 15th Century, clocks were able to go portable for the first time. They would gradually reduce in size until pocketwatches first began to appear in the 17th Century. The invention of the balanced spring and addition to clock balance wheels in the mid 17th Century greatly improved timekeeping device accuracy. Despite these advancements, pendulum clocks remained one of the most accurate clock designs well into the 20th Century. Microelectronics began to appear in the 1960s and were first used in laboratories. These made quartz clocks more compact and much cheaper to manufacture and produce. By the 1980s they became the world's dominant timekeeping technology in both clocks and wristwatches.
The reputation Cartier has towards being an incredible watchmaker is almost fixated in the minds of watch collectors, and buyers for close to over a hundred years. Many might be surprised to know that they also have a high reputation for being clock makers as well. reputation as a watchmaker has been secure in the minds of watch enthusiasts for probably close to a hundred years, but its clockmaking has always been a bit more in the background. While for most of its history Cartier watches were quite exclusive as well its clocks have always been something for connoisseurs and rather more out of the public eye than in it.
Cartier has generally treated clockmaking as an area in which to exercise its capabilities in design as much as possible and as a master of decorative arts. Cartier clocks have often been horologically innovative as well. Even mechanically simple Cartier clocks are works of decorative art, often with elaborate engraving and enameling. Its most complex clocks include the famous "mystery" clocks, in which the hands of the clock are suspended in transparent panes of rock crystal and move with no apparent connection to any mechanism.