The company has already sold 3.5 million of these tiny but mighty lamps around the globe. And for good reason. With a day of charge under sunlight, the lamp can stay illuminated for 45 hours straight. It's clearly not one of those gimmicky solar lamps that only show promise but no performance. But since it isn't ever going to be dark for 24 hours, the lamp serves other purposes too: You can charge your phone from the inbuilt USB port. It can serve as a great travel companion too; just as long as the weather forecast predicts clear blue skies.