Gram to milligram is a unit conversion that represents the change in mass from the gram (g) to the milligram (mg). The gram is a unit of mass in the International System of Units (SI), equivalent to one thousandth of a kilogram. On the other hand, the milligram is a smaller unit of mass, equal to one thousandth of a gram. This conversion is crucial in various scientific and practical applications, such as measuring the weight of small objects, calculating the dosage of medications, and determining the concentration of solutions in chemistry and pharmaceutical industries.