Probiotics are live microbes which, when administered in sufficient amounts, confer a health benefit to the host. According to recent clinical trials, administration of probiotics to very low birth weight infants significantly reduces overall mortality and risk of necrotizing enterocolitis, a devastating inflammatory intestinal disease. The investigators have previously demonstrated that administering probiotics to the lactating mother enhances the immunoprotective properties of breast milk. Despite the promising data, the optimal probiotic intervention is yet to be established. The mechanisms by which probiotics exert their effects remain largely unknown.