A microchip is a tiny electronic device, about the size and shape of a grain of rice, that is implanted beneath a pet's skin between the shoulder blades and stays there for the pet's entire life. This procedure is as easy and as painless as a vaccination.
Each microchip has a unique number. This number, along with information about the owner and pet, are added to a national pet registry. Most veterinary hospitals and animal shelters have electronic scanners for detecting and reading these implanted microchips. If a lost pet is found and a microchip is scanned, the registry is called and the owner can be contacted.
Here's a success story about microchips of our own:
Cami was a pregnant dog that was taken in by the local Kankakee County Humane Foundation and then was fostered by one of the Foundation members. Shortly after she weaned her puppies, she ran out of the backyard and did not return. Six months later, a family that lived across the river coaxed Cami to come inside their house. Their veterinarian scanned for a microchip, which was traced back to the Foundation. After all those months everyone involved with Cami breathed a sigh of relief that she was safe and placed in a good home.