take all of those numbers, put it on a computer screen, and tell us where the hot spots are and just how high the levels got. my cell phone measured within fcc limits. but the whole process was surprisingly low tech. what about different size skulls or children? >> in children, their skull is thinner, so the microwave radiation can penetrate deeper into the brain in children and young adults. and their cells are dividing at a much faster rate. >> reporter: but there have been no studies on chirp and cell phone safety. and the cell manufacturers advise putting the cell phone next to your head or on your body. take a look with the iphone 4, the safety instructions say when using the iphone near your body, keep it at least 15 millimeters away from your body.