 formula,"I was looking for a formula to supplement my breastmilk for my twins (I have never made enough). I was given Similac Advanced in the hospital in the little two ounce bottles, so I started there. When we ran out of the free samples, we tried to switch to the powdered Similac Advanced, it gave my girls horrible gas. I didn't realize that the two might be different. When we went back to pre-mix to try to resolve the gas issue, I bough a couple of bottles of the organic to try out. I felt 