Anyone who has taken a basic chemistry of physics course can tell you that the only way to get steam from water is to boil it. As published in the American Chemical Society's journal ACS Nano, researchers have found a way to generate steam without boiling water, or at least not much water. The key was using nanoparticles in a novel way.
Nanoparticles have been looked at for many uses, including generating electricity from sunlight, but no one had yet looked at using them to generate enough heat from sunlight to generate steam. That is exactly what the researchers did as they added different kinds of nanoparticles to water and then put the mixture out in the sun. As the sunlight hit the nanoparticles, they heated up to above the boiling temperature of water, causing a buildup of vapor around the particle, until it eventually escaped. In the case of some silicon dioxide/gold nanoparticles, the vapor escaped in "microexplosive burst" within 5-20 seconds of being exposed to sunlight.
This discovery could have major impacts across the globe, especially as it is optimized, for purifying water and cleaning up different kinds of waste. Potentially, if it can work at higher pressures and with liquids other than water, this technology could even be used to more efficiently generate electricity by using the steam to turn turbines.