A microgram is a unit of mass equal to one-millionth of a gram. It is often used in scientific contexts, particularly in fields like chemistry and medicine, to measure very small quantities of substances. For example, vitamins and medications may be dosed in micrograms to ensure precise amounts are administered. In the metric system, the symbol for microgram is µg. This measurement is crucial for understanding the effects of certain compounds, as even tiny amounts can have significant biological impacts. For instance, the recommended daily intake of some vitamins is often expressed in micrograms to reflect the small amounts needed for health.