杯中貓-美國體型最嬌小的貓 在貓群中不斷找尋體型最嬌小的個體繁殖而來. "Miniaturisation by progressive downsizing is neither dwarfism nor midgetism, but is the result of always breeding from the smallest individuals in a population. In most animals there is a natural variation in size - a few unusually large individuals, a few undersized ones and the majority being "normal size". Some simply turn out smaller than other due to the interaction of various genes. By breeding only from the smallest individuals, it is possible to create a population of undersized animals."