Mobile phones give off electromagnetic radiation. Although these radiation fields are quite weak, we use our phones a lot so we have a high level of exposure. In Finland, 80% of people have a mobile, so researchers looked into the health risks, testing the effects of phone radiation on cultured cells and small animals. The phone waves appeared to stress the cell cultures, but didn't increase the likelihood of cancer in animals. But in combination with other nasties like UV light, there may be cumulative effects. When they tested phone radiation on peoples' brains they found an effect on the electrical activity of the brain, but this didn't affect brain function. The scientists are now trying to find out nexactly how much radiation we really receive from our mobiles, and how much it can penetrate into our brains and bones. In the meantime, it's best to limit your exposure- but that's probably not what the phone-mad world wants to hear.