There are 1 million microseconds in one second. Microseconds are part of the International System of Units, otherwise known as the SI system. The SI system is managed by the International Bureau of Weights and Measures.
The SI system contains seven basic units of measurement. These are the meter, kilogram, second, ampere, Kelvin, candela and mole. An additional prefix can then be added to the base unit in order to provide a degree of magnitude. For example, the prefix milli- signifies 10 to the negative third power. Therefore, a millisecond is a length of time equal to one second multiplied by 10 to the negative third power, or one-thousandth of a second.