A Stopwatch is a hand held timepiece which is specifically designed to measure the amount of time elapsed from a particular time when activated to when the piece is deactivated. Traditionally the timing functions on a stopwatch are controlled by two buttons on the case. With functions such as split and lap timing, which are all controlled with the two button functions. Mechanical stop watches are powered by a main spring, which must be wound, with digital electronic stop watches being seen as much more accurate timepieces due to their crystal oscillator, with day,date and time functions also often being included in the digital stop watch functionality. Stop Watches are mainly used when the time period is needed to be measured precisely without complications, with laboratory experiments and sporting events being good examples of where they are commonly used.