Bertrand Piccard co-founded with André Borschberg the Solar Impulse project to build this – the world's most advanced solar airplane and the coolest thing on two wings (apologies, hummingbirds). In June 2012 the carbon-fibre HB-SIA – as wide as an Airbus A340 but lighter than an Audi A6 – completed the world's first solar-powered intercontinental flight. That's just the start. Work starts on its successor, the HB-SIB, later this summer, with a round-the-world flight pencilled-in for Spring 2014. Because the Solar Impulse's cells both propel its flight and charge its batteries, it could theoretically stay in the air indefinitely.