A urine power source has produced enough electricity for scientists to make a "brief" mobile phone call.
Scientists at the Bristol Robotics Laboratory in Britain are claiming the development as a world first.
They said the technology had the potential to be installed into bathrooms to harness urine to produce enough electricity to power showers, lighting or razors.
So far they have managed to charge a Samsung mobile phone with enough electricity to send text messages, browse the web and make that brief phone call.
"The concept has been tested and it works," researcher Dr Ioannis Ieropoulos said.
Researchers at the laboratory - a collaboration between Bristol University and the University of the West of England - generated electricity by passing urine through a cascade of microbial fuel cells (MFCs).
In the MFCs microbes produce electricity as a by-product when they eat urine.
"This is the first time we have been able to directly charge the battery of a device such as a mobile phone and it is indeed a breakthrough," Ieropoulos said.
The goal now was to develop and refine the process to get MFCs to fully charge a battery.
"Using the ultimate waste product as a source of power to produce electricity is about as eco as it gets," he said.
"We are currently bidding for funding to work alongside partners in the US and South Africa to develop a smart toilet."
The research was published in the journal Physical Chemistry Chemical Physics.