Kittens come into the world with their eyes and ears closed and spend the first week or so of their lives blind and deaf. Their eyes open during the second week, but their vision isn't very good at this point, and they'll need to be kept out of bright light, says The Spruce Pets. The blue eyes that kittens are born with may start to change color during their third week, which is also when their ears begin to open and perk up, introducing them to a whole new world filled with sound.

Kittens have the ability to make sounds from birth, and may be heard making little mews to let their mother know they're hungry, says Catster. Purring typically begins during week three, and kittens tend to become more vocal as they start being able to walk, play and explore their surroundings.

The Fédération Cynologique Internationale (FCI), also known as the World Canine Organization, is an international federation of kennel clubs from 84 countries worldwide, excluding the United States, the United Kingdom, and Australia. In these countries, the respective governing bodies for determining dog breeds and breed standards are the American Kennel Club (AKC), British Kennel Club (KC), and Australian National Kennel Council (ANKC). These organizations are responsible for determining which dogs meet the qualifications of a breed, as well as for establishing and enforcing breed standards in each of the regions they serve.

It's a fairly long road for a new type of dog to become an established breed. The various breed associations may differ slightly on how they determine the recognition of a new breed. However, they all generally follow the model of the AKC, which requires that there is a significant enough population of a particular type of dog and enough national interest to justify breed recognition. Establishing a breed also means looking out for the health and characteristics of that kind of dog and establishing rules to make sure breeders are raising healthy dogs safely and ethically.

Before the AKC considers a new breed for purebred status, the new breed must have a population of at least 300 to 400 dogs, spanning a minimum of three generations. There must also be a national kennel club devoted to this new breed that includes at least 100 members spread out over no fewer than 20 states. The club must also have an established set of standards and qualifications that a dog must meet to be considered part of the breed.

There is a wide number of dog breeds. In the United States alone, the AKC's dog breed list currently includes 200 dog breeds. Worldwide, the FCI lists 360 officially recognized breeds. These don't include experimental breeds that have yet to achieve official status. Official lists also don't include mixed-breed dogs, not even "designer" crossbreeds like the Goldendoodle (a cross between a Golden Retriever and a Poodle) or the Puggle (a mix of Beagle and Pug).

As cute and as popular as these hip new pups are, the fact that they're mixed breed dogs with no established standards outlining their appearance and characteristics for health disqualifies them for purebred certification. As with any wildly popular breed, prospective parents should work to make sure a puppy is healthy and a breeder is ethical before purchasing a dog. And all breeds of dogs that wind up at your local animal shelter could end up being your forever friend.