Why Relationships?

As an introverted observer of people throughout my life, I wonder what makes relationships...Relationships. There is a myriad of reasons why they work and why they don't work - things that we see everyday. My question is simply why? The aim of my blog is not only for the academic assignment, but also a personal delve into getting some answers (fact and opinion) and testing some theories on the how's,why's,and whats the deal with relationships: What makes them "tick", what are they made of, and why are they?