Women in costumes walk as they participate in Halloween celebrations in the downtown of Seoul, South Korea, October 31, 2015. (Photo by Kim Hong-Ji/Reuters)

The Photographers 2015 runs from 25 November to 23 December at Osborne Samuel and Beetles+Huxley, London. Here: Untitled, 1950, by Bert Hardy. (Photo by Bert Hardy/Beetles+Huxley & Osborne Samuel)

Ricardo Azevedo rides his Honda NX 200 motorbike, which he converted to be powered by water, in Salto, northwest of Sao Paulo, Brazil, August 6, 2015. The Sao Paulo civil servant built the motorbike, which can cover up to 500 kilometres (311 miles) fuelled by just one litre of water. Dubbed “Moto Power H2O” the bike is powered by the process of electrolysis, which breaks the water molecule down into its constituent elements. (Photo by Nacho Doce/Reuters)

In this Wednesday, March 18, 2015 photo, limestone quarry workers walk through a cloud of dust spewed into the air by rotor blades of the stone-cutting machinery in the desert of Minya, southern Egypt. Around 45,000 people, including children, work in an estimated 1,500 quarries, digging out stones that later will be used in construction or powdered to be used by pharmaceutical and ceramic companies. (Photo by Mosa'ab Elshamy/AP Photo)

A 14 year-old Myanmar girl carries three bags of powdered-limestone to load in to a boat on the bank of Ayeyarwaddy River, on International Women's Day in Mandalay, Myanmar, Tuesday, March 8, 2016. Migrant workers living along Ayeyarwaddy riverbank earn bout 5000 Kyats (US Dollar 4) a day for loading and unloading goods. (Photro by Hkun Lat/AP Photo)

A fighter of Libyan forces allied with the U.N.-backed government runs for cover during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

Russian marines attached to the anti- submarine ship Admiral Tributs show their skills during a demonstration at a park in Manila on January 5, 2017, as part of their five- day port- of- call activities in the country' s capital. (Photo by Ted Aljibe/AFP Photo)

“Winter shapes, Moscow river”. Moscow river at this part is never covered by ice. When the temperature is very low it's possible to see a strong fog. Morning light and pipes of the oli factory creates a fantastic landscape. Photo location: Moscow, Russia. (Photo and caption by Sergey Rumyantsev/National Geographic Photo Contest)