Her sense of smell
A cat’s sense of smell plays a large role in her behaviour. That's why when two cats meets for the first time, they sniff each other's noses. While hunting, cats don't rely much on their sense of smell, even though it’s more developed than in humans.
A cat marks with her scent glands on both sides of the head near the chin, on lips and tail. Scent marks are left on trees, objects, other pets and even humans. We cannot smell this substance. Cats, however, take it as a sign of friendship. Intact tomcats also leave scent marks with their anal glands, which unfortunately, is a lot easier for humans to pick up.