An update on the life inside you

There's a recount on that report that 90% of the cells in your body are not human. Tabitha M. Powledge writes that a new report says the ratio may actually be much lower: "I am a bit mournful about this development. The idea of 10 microbes to every human cell is so much cooler than only 3 to 1. I am wondering if I will have to find a new favorite statistic." Also, Twitter as a gauge of scientific impact, and Vitamin E for slowing Alzheimer's.