Many centuries ago, man was able to tell the time by looking at the sun and its position in the sky. Then came the sundial and finally the clocks and watches. The actual purpose of the watch as we all know is to tell us the time down to the tenth of a second. Watches with heart rate monitors are exercise watches that will monitor and let us know the heart rate while we exercise. Before the advent of the wristwatch, all mobile watches that could be carried around were pocket watches. They were attached to a chain or rope and were kept in the pocket. Like with everything else, watches have evolved with time. There are mechanical watches, battery, solar, and kinetic powered watches. Mobile watch, ie. the wristwatch was popularized and materials used for the straps are all metals, including materials like leather. Sapphire crystals are used in watches to improve the quality and durability. Electronic watches with quart movements are mainly used these days. They do not need batteries and get charged with movement of the wrist. A mechanical watch does need winding up but lasts longer. Now, people also look at the style and design of the watch. There are specific watches made for different purposes.