"Teacup" is not a breed
No kennel club recognizes "teacup" dogs. The word is a sales label for unusually tiny Chihuahuas, Yorkshire Terriers, Pomeranians, Maltese and Poodles, often bred from the smallest, weakest dogs in a litter. Veterinarians warn that tiny dogs are prone to dangerously low blood sugar, fluid on the brain (hydrocephalus), an open soft spot in the skull, liver shunts, a collapsing windpipe, and bones that break in a short fall.
Smaller is not always cuter for the dog. A higher price for a smaller dog rewards breeding that harms dogs.