The Chihuahua is the smallest of all dog breeds and they have become extremely popular over time. This dog is claimed to have originated from Chihuahua, Mexico and (this is shocking) at first was bred mostly to be eaten. However, when the Aztecs conquered the region, these dogs were believed to be able to see the future and cure disease by taking on the sickness themselves. Every household owned a red Chihuahua, the designated dog to bring souls to the underworld.
After the Spanish arrived in Mexico, little attention was paid to the dogs. Most of them became feral and survived off of birds and other small animals. The restoration of this dog’s popularity took a long time: It was not until 1946 that first independent Chihuahua specialty show occurred in the US. 
The American Kennel Club as well as the Kennel Club in the United Kingdom recognize only two major varieties of this breed, the long haired and the short haired (which latter is sometimes referred to as the smooth-coat). The most common colors of the Chihuahua include black, white, brown, red, cream, fawn, and chocolate. This is one of the few breeds where each color is considered neither better or worse than the next in show competitions. 
Despite their size, these dogs possess innate intelligence that often impresses their owners. The Chihuahua can get along well with children who are calm and respectful. However, some Chihuahuas are genetically ill-tempered and should not be living with children.
Nonetheless, the breed is loved by many because they are plucky, agile, and cheerful. These characteristics have helped push this dog up the popularity chain.
It is very common for a Chihuahua to develop a deep bond with only one singular person. They are known to be overprotective of their owners, sometimes becoming aggressive when other animals or people are around.
This small breed is also known to be fun-loving, bold, curious and affectionate. They are fast learners. In fact, they are able to compete and win against some large dogs in obedience and agility trainings. Chihuahua owners have reported that this dog may become willful, but with adequate training this can be overcome. Owners are also recommended to use only positive reinforcement while training their Chihuahua.
Chihuahuas can actually be wonderful watch dogs. They are able to alert their family when any stranger is approaching. When trained to socialize, they can interact well with children and other animals. However, they usually do not trust strangers.
This dog breed can do well in apartments. They also love warm environments and dislike being kept in small and cold places. Chihuahuas need at least 20 minutes of exercise daily. With a proper diet, ample exercise and regular grooming Chihuahuas can live 12 to 17 years. 
 D. Caroline Coile, The Chihuahua Handbook (Barron’s Educational Series, 2010). 5-8.
 Jacqueline O’Neil, Chihuahuas For Dummies (John Wiley & Sons, 2011). 30.
 Elaine Waldorf Gewirtz, Chihuahua: Your Happy Healthy Pet (John Wiley & Sons, 2006). 23.