Essential nutrients for development from conception to old age are described here. Focus lies on critical windows of development or life stages with changed needs – such as pregnancy and lactation, sometimes associated with certain pathologies. For infants, vitamin and mineral concentrations in mother's milk are commonly taken as guidance to determine a healthy infant's nutrient need. However, the high variation of human milk composition does not allow for a universal standard of target values; therefore science collects ranges of the various nutrients that were reported in different populations, countries, continents, climate and more.