Two attendees compete in the biggest vape cloud competition at the Vape Summit 3 in Las Vegas, Nevada May 2, 2015. According to new research provided to Reuters, youngsters say that performing tricks is one of the top two reasons they began using e-cigs. (Photo by David Becker/Reuters)

“Mr Big Dipper”, Nicholas Roemmelt (Denmark). A stargazer observes the constellation of the Big Dipper perfectly aligned with the window of the entrance to a large glacier cave in Engadin, Switzerland. This is a panorama of two pictures, and each is a stack of another two pictures: one for the stars and another one for the foreground, but with no composing or time blending. (Photo by Nicholas Roemmelt/National Maritime Museum/The Guardian)

Tandem hair drying is possible with a new two-hood attachment for any electric hair dryer manufactured by Postcraft Co of Tucson, Ariz., shown in Chicago, January 27, 1965. A Y adapter permits two hoses to be attached to the dryer. (Photo by Edward Kitch/AP Photo)

Janus, a two-headed Greek turtle named after the Roman god with two heads is testing a kind of skateboard to rehabilitate one day ahead of her 25th birthday at the Natural History Museum in Geneva on September 2, 2022. (Photo by Pierre Albouy/Reuters)

One of the two one-year-old albino alligator is seen in a vivarium at the Tropical aquarium in Paris. The two alligators are the result of a captive breeding program which protect endangered species and will presented to the public in a vivarium. (Photo by Philippe Wojazer/Reuters)

A policewoman uses her mobile phone as navy honor guards stand near of a World War Two memorial during celebrations to mark Victory Day in the Black Sea port of Odessa May 9, 2014. Ukraine celebrates the 1945 victory over Nazi Germany during World War Two on May 9. (Photo by Gleb Garanich/Reuters)

The newly-discovered gaseous planet Kepler-16b orbits it's two stars. NASA's Kepler Mission discoverd the world orbiting two Stars, the larger a K dwarf and the smaller a red dwarf. (Photo by NASA/JPL-Caltech/T. Pyle via Getty Images)

Canadian-Israeli film director Simcha Jacobovici holds two nails during a press conference on April 12, 2011. Jacobovici believes that the two nails discovered in a Jerusalem cave were used in the crucifixion of Jesus Christ. Jacobovici claims that the nails were tracked to an archeology laboratory in Tel Aviv, and though cannot be 100 per cent certain that they are the nails used in the crucifixion of Jesus, he claims if “you put two and two together and they seem to imply that these are the nails”. Experts at the Israel Antiquities Authority though cast doubt on Jacobovici's claims, and suggest that nails are commonly found in such locations. (Photo by Lior Mizrahi/Getty Images)