For example, let's suppose we take this first beaker. We add the hydrant to it and we heat it. And so this will turn dark blue or dark purple. And then we take a pipette. We take a small sample out of that mixture, and we place it into a special apparatus that is able to absorb light or determine how much light is actually absorbed. And so we shine light at a specific wavelength, it absorbs them, and we determine how much is absorbed.