Plastic bottles filled with water
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How water bottles create cheap lighting in Philippines

A simple initiative in the Philippines is bringing a bit of brightness into the lives of the country's poorest people.

The project is called "Litre of Light", and the technology involved is just a plastic bottle filled with water.

It's an environmentally-friendly alternative to an electric light bulb, and it's virtually free.

The BBC's Kate McGeown reports from Manila.