Light is one of those basic things like food, safe water and even air, that we don't notice until we don't have it. Some days, refugees in a camp called Kiziba in western Rwanda have had to trade food rations for candles to light their homes at night. But not anymore. Now, the Global Brightlight Foundation has distributed Sun King solar LED lamps to 3700 households in the camp, and the result has been eye-opening. The video below tells the story and might even bring a tear to your eye. But first, here is the back story that could make it more meaningful.

The camp's residents fled the Democratic Republic of Congo during its civil war in 1996 and took shelter in Kiziba. Now nearly 20 years later, 16,000 of them remain, working in homegrown businesses and supplementing their livelihoods with food rations and other goods from the UN High Commission for Refugees (UNHCR) and charitable organizations.

One of the ways to measure how useful a thing is to the residents is to calculate the percentage of those things that they sell. Because they have so little, the refugees sell much of what they are given to the Rwandan communities nearby or trade it with others in the camp. When the solar lights were introduced, the refugee camp manager estimated that at least 30 percent of the people who received a light would sell it for something else, maybe for shoes, clothes, vegetables or whatever else they need. But that has not happened.

Instead, less than 1 percent of the lights have been sold, says Sam Dargan, head of Great Lakes Energy, which markets solar lights in Rwanda and works with Brightlight. But the story gets even better.

Periodically, the United States allows groups of 15 refugees to emigrate and settle within its borders. Usually the refugees sell everything before they leave to make some cash for their move. But now there is one thing that they don't sell. Two groups have left Kiziba since the lamps were distributed, and both have returned every one of the lamps they had received to the UNHCR with the instructions that the lamps should be used by other families who are staying behind. That's how important light is, so useful that it must be shared.

This video tells the story. Watch it, and if you're in a sensitive mood, have a tissue nearby. This is “Darkness Was Gone.”

Darkness Was Gone from What Took You So Long? on Vimeo.