Teacup puppies refer to dogs that are bred to be much smaller than the average size for their breed. This trend has become popular in recent years, particularly with small and toy dog breeds. The term "teacup" is often used to describe dogs that are extremely tiny, typically weighing less than 4 pounds when fully grown.

It's essential to note that the concept of teacup puppies raises ethical concerns within the breeding community and among animal welfare advocates. Achieving such small sizes often involves breeding from the smallest dogs within a litter, which can lead to various health problems for the animals. Teacup dogs may be more prone to congenital defects, developmental issues, and a higher risk of injury due to their fragility.