First came vitamins. Cod liver oil was added, and mixtures of fats from a variety of sources. It took a while for people who were using the easy and cheap option of evaporated milk formula to get interested, but by the 1950s, proprietary formulas like Similac, which had been invented in th1920s, were starting to gain steam. Formula became not just a stopgap, but a kind of superfood, capable of delivering a kaleidoscope of nutrition.