Scientists at Bristol Robotics Lab in the UK have worked out how to turn urine into electricity.
A collection of cylinders is filled with electro-active micro-organisms.
They feed off things they find in waste water and urine.
Electrons are created as a by-product, which can then be turned into electricity and used to charge phones and power some lights.
BBC Click went to find out more.
See more at Click’s website and @BBCClick.