Here's how it works: You place your raw fish on the plate and see if the LED rings around the outside light up. If the white LEDs light, it means there is radiation in your fish, but a safe level. If the red LED rings glow, you might want to consider a hamburger instead. I'm not so sure I'd use this as my daily dinner plate, but if I had one I guess I'd keep it near the fillet board on my boat for quick screenings before dropping the day's catch in Zip-Loc bags. In case you were wondering, the radiation meter on the underside of the plate is removable, and the rest is dishwasher safe. Have a good weekend.