Humans have 5 million olfactory cells, while cats have more than 240 million olfactory cells, which is more than 40 times that of humans. The human olfactory area is about 10 square centimeters, and the cat’s olfactory area is 20 ~40 square centimeters, which is 3 times that of humans in terms of smell area. In terms of comprehensive sensitivity of smell, cats are 80 times that of humans. ​​​​​​

Cats leave their marks through their sense of smell. When entering a strange environment, cats will smell everywhere to spread their own scent and become familiar with the surrounding environment. When cats find unfamiliar things, they will also smell them to leave their own scent and mark their territory.

Cats can know the gender of other cats and whether they are in estrus just by smelling the urine and odor glands of other cats. Sweat and sebum make the nose mirror moist, so odor molecules can easily adhere to it, sharpening the cat's sense of smell.