It's the unexpected beginning of something new. Something good just comes into your messed up life without an alarm .You come across somebody in the middle of your busy life , just someone you have no idea is going to stay or leave.
It also is the most causal and effortless stage of a relationship. When you just want to be a part of someone's life even if it's a small part.
This stage is of happiness. It comes when you think you're really going to connect with someone after along time, Someone who is just your type, maybe.