New technology is being developed using sound waves. These sound waves can burn away tumors and other unwanted things without harming the tissue around it. This works because many sound waves are being shot from different directions. The friction is only enough to cause enough heat to affect anything where they intersect. For instance, if someone has a tumor in their brain that is surrounded by certain parts of the brain that cannot be touched, the sound waves would just go through the sensitive parts of the brain and burn away the tumor. I just thought this was a cool new technology.