Why do you cry?

Have you ever wondered why do people cry? Some people cry for joy, some other cry for sadness. Have you ever cried no heard you cried? Have you ever cried with no tears. Do you cry for a purpose? Do you cry just because you're being emotional? Are you a cry baby? Why tough people cry? Why people with big money cry? What do you do when you see someone cry? Do you ever see someone cry with no tears in their eyes? Do you cry because of physical pain?