Today's Health|Science: humans and their microbes, Antarctic penguins, violence and mental illness, letting perfect go

Scientists estimate that 90 percent of the cells contained in the human body belong to nonhuman organisms - mostly bacteria, but also a smattering of fungi and other eensy entities. Some 100 trillion microbes nestle in niches from our teeth to our toes. They may be so essential to well-being that humans couldn't live without them.

Antarctica's beloved king penguins may be facing a climate catastrophe. In a recent study in the Proceedings of the National Academy of Sciences, researchers say the populations - now at more than 2 million breeding pairs since rebounding from near extinction in the last century - could collapse as the surface temperature of the Southern Ocean warms.

In recent weeks, the news has been full of horrendous stories involving killers with known or suspected mental illness. Yet the impression that we are awash in a sea of psychotic violence is clearly unfounded.

After more than 20 years of studying women's health issues, psychologist Alice Domar (left) has come to a grand conclusion: Women are just too hard on themselves. There is no pill that will cure this self-imposed pressure - which Domar says creates harmful stress and makes dealing with everything from eating disorders to infertility more difficult. People will take pills, Domar says. That's easy. What's hard is to get women to accept what she says is obvious to men: Perfection is not attainable.

Also, are oats really as good for you as we are told and those flashlights that you shake to charge - how do they work?