There are two different brands of widely used microchips out on the market. They are AVID (which someone mentioned already) and HomeAgain. Both are used by vets, shelters, rescues, etc. They are actually almost identical in natural. They are inserted under the skin (like a SubQ injection) using a needle usually near the shoulders. The microchip itself is roughly the size of a piece of rice. Each microchip has a unique number that can be read by a scanner through the animal's skin. The scanners that I have seen and used are a little longer and skinner than a box of checks. There is usually a fee for having the chip registered to you with your name, address and phone number. But the fee is relatively small...under $20, with different fees for multiple pet registeration. The chip is automatically registered to the vet clinic or shelter that purchased the chips and most places keep a record of which chips went into which animals. So even if the chip isnt registered into your name and you lose the animal...they can still say well it was sold to so and so. This is however, not the most ideal situation because of the roundabout tracking that is needed to be done. I have 3 ferrets and a puppy microchipped. 2 have HomeAgain and 2 have AVID. While not having lost any of my critters, I cannot say I have "tested" how this works, but I have scanned and used it at the emergency clinic I worked at for a stray someone brought in. You can have this done while your critters are awake. I believe that most vets do it in this route, although I do know that some of them prefer to do it while the critters are under so there are no squirming misses. All of my critters were under when it was done, as a matter of choice for my ferrets (because they squirm) and done while my puppy was getting neutered. Again the microchips are not a "tracking" device for you to look for your ferrets when they have disappeared but a permenant form of identification when they are lost and need to be identified. There are websites for more information at www.avidid.com and www.homeagainid.com. Stephanie g. 3 fuzzies and a ferret herding puppy [Posted in FML issue 4070]