People in the Philippines have found a primitive, but also very clever way to bring light into their home. They make a hole in the roof, where is placed a plastic bottle filled with water and disinfectant. When sunlight hits the bottle, it is scattered around the room. They add few tablespoons of bleach to keep the water clean. Such a device can operate for about five years. This invention was a real relief for people who live in poor areas, because they had lived in the dark or the light of kerosene lamps.