The time from conception to a child's second birthday is the most important 1,000 days of their life, as these initial months are vital developmental periods during which babies' brains and bodies need the right fuel to grow. Providing infants with the best possible nutrition during these early days is important - whether parents choose to breastfeed, formula-feed or both. If you don't breastfeed, parents can still feel confident that baby will get the best nutrition.