Ann Makosinski, a 15-year-old student with Canada’s St. Michaels University School, has created a flashlight that is powered solely by the heat of a human hand. For this, she has been chosen as one of 15 finalists for Google’s global science fair.

She created the device using the idea of Peltier tiles, which are devices that create energy when one side is heated while the other side is cooled. Combining this, which created enough power, with a store-bought circuit, which provided enough voltage, she ended up with The Hollow Flashlight. Inside the flashlight is nothing but air, which acts as the cooling agent. So, wrap your hand around the outside, and you’ve got the necessary temperature duality.