Coloured X-ray of a barn owl. A physicist has used X-ray to create an extraordinary collection of artwork. Arie van't Riets pictures reveal birds, fish, monkeys and flowers in an incredible new light. The 66-year-old, from Bathmen in the Netherlands, began X-raying flowers as a means to teach radiographers and physicians how the machine worked. But after adding a bit of colour to the pictures, the retired medical physicist realised the potential for an exciting new collection of art. (Photo by Arie van't Riet/Barcroft Media)

Women dressed in folk costumes take part in a traditional wedding ceremony in the village of Galicnik, west of Macedonia's capital Skopje, July 12, 2014. The Galicnik Wedding, a three-day traditional Macedonian wedding celebration held each “Petrovden” or St. Peter's Day, involves traditional customs, costumes, and rituals and dances that have been passed down over the centuries. (Photo by Ognen Teofilovski/Reuters)

Amundsen-Scott South Pole Station experiences months of darkness. The sun dips below the horizon on March 21, after which follows several weeks of twilight before complete darkness results. Photo taken on June 25, 2009. (National Science Foundation/Jeremy Johnson)

American film and theater actress, singer and dancer Shirley MacLaine. (Photo by Philippe Halsman)

Members of the Communist New Fourth Army on parade. Note how the modern equipment contrasts with the shoeless soldiers in the foreground. (Photo by Hulton Archive/Getty Images). 6th July 1946

An employee of the National Park Service takes a selfie with President Barack Obama, left, in the background meeting with the crowd after a tour of Everglades National Park on Earth Day, Wednesday, April 22, 2015, in Florida. Obama used the visit to warn of the damage that climate change is already inflicting on the nation's environmental treasures. (Photo by Lynne Sladky/AP Photo)

A Buddhist monk catches an aerial view of Kathmandu from the damaged Swayambhunath Stupa premises in Kathmandu, Nepal, Wednesday, May 6, 2015. The April 25 earthquake killed thousands and injured many more as it flattened mountain villages and destroyed buildings and archaeological sites in Kathmandu. (Photo by Niranjan Shrestha/AP Photo)

An injured NATO soldier lies on the ground following a suicide car bomb attack that targeted foreign military vehicles in the Afghan capital Kabul on June 30,2015. A powerful blast hit downtown Kabul on June 30 as a suicide car bomber targeted foreign military vehicles, officials said, with casualties feared. The blast came on the main road to the airport, around 500 meters (550 yards) from the US embassy and near a base for foreign troops.“It was a suicide car bomber targeting a convoy of foreign forces in Kabul”, interior ministry spokesman Sediq Sediq said. (Photo by Wakil Kohsar/AFP Photo)