What Makes a Person Experience Joy?

It is still unclear what exactly makes a person laugh and have fun. After all, senses of humor differ. Scientists believe that laughing is necessary to balance the mental processes, such as to relieve stress, worrying and angst. Laugh produces natural intoxicating substances – endorphins and antidepressants.

Humans simply cannot live without enjoying beautiful things even if they have no utilitarian purpose. Why does it happen?