The idea is simple, the impact immense: Illac Diaz, a former actor from the Philippines, is bringing light to the slums of his home country’s capital Manila just by using humble discarded plastic bottles. An old bottle is filled with water and a small quantity of bleach is added to sterilize the liquid and keep it clear. The bottle is then vertically wedged into a hole cut in the corrugated iron of a hut roof, secured to stop it from falling down and sealed with a bit of rubber. The makeshift bulb is ready. When the sun outside shines on the bottle, the water inside it refracts the light and illuminates the interior of the hut without the use of electricity.