Breast milk is truly an amazing thing, and far beyond anything that we can do to replace it. It even adapts to the specific needs of the baby. I recommend this long fascinating article if you're at all interested:
The Stranger: The More I Learn About Breast Milk, the More Amazed I AmI realize not all moms can breastfeed, and our society is often making it way harder than it should be. I'm just grateful that my two daughters have had the luxury of starting life with long periods of breastfeeding (the first one 20 months, the second still going at 15 months). Something that may have even more benefits than those mentioned in the article.