What might leak from underneath exhaust pipe area? Just behind back left wheel...

I've noticed a small puddle every morning from while it's been sat overnight...

 

what color is the fluid? Do you have ACE, or rear heat? Could it just be condensation from the exhaust?

More information is better.

 

No, don't have ACE. No rear heat. Took a glance under there... everything looks fine. But there is a puddle every morning about 1 feet x 1 feet big.

The puddle has that rainbow coloration to it, indicating that it's probably fuel (or an oil of some kind).

 

Does it smell like fuel? Does it feel oily or is it water picking up a shimmer from old oil on the garage floor....