Probiotics is the name for beneficial bacteria in our guts and on our skin. And prebiotics is the name for things, foods that nourish the good bacteria in our guts. It turns out, for most of human history, we were getting probiotics sort of automatically. Whenever someone visits a farm, they collect more beneficial bacteria that end up in them - it's not surprising. There are studies showing that if you visit a farm even once before the first birthday, your lifetime risk of asthma is lower, just by doing that one thing. But in recent industrialized society, as we move away from the farms, into the cities, since we've got chlorine in our water to kill infections, as we got antibiotics being prescribed so often for children and as we're eating so much food that's junk food, we've lost a lot of the good bacteria in our guts. It turns out, giving probiotics to pregnant women, to nursing women and to children, can be really beneficial. I recommend it for everybody when they take antibiotics, but it's good other times as well. And some of the benefits that have been shown is you can decrease eczema, for instance, in kids if their mom or the baby gets probiotics. You can also decrease allergies in general. One of the most interesting things that I found recently was the study of giving probiotics versus placebo in preventing flu. And what they showed was that getting probiotics was about as effective as a flu shot at preventing flu. Healthy bacteria are part of us. There are about 10x as many bacterial cells in our body as our own cells, so it makes sense to have ones you really want to be friends with.