Lots of relationships grow out of an initial attraction (a crush or "love at first sight") and develop into closeness.
Research shows that the majority of these relationships remain purely for sex –and that this often has no negative effect. Reeder told us, studies show “that having sex with a friend once or twice doesn’t damage the friendship”.
Read more: Top ten tips for an office romance But does this tell the whole story?
Love is such a powerful human emotion that experts are constantly studying it.
They've discovered that love has three main qualities: These three qualities of love can be combined in different ways to make different kinds of relationships.
Teens all over the world notice passionate feelings of attraction.