The photographs feature fish that have been specially treated to make the stained skeletal tissues visible through the skin and flesh. The technique, developed by Dr. Adam Summers, uses dyes, hydrogen peroxide, a digestive enzyme and glycerin to make the flesh seem to disappear. Photo: This image of the butterfly ray (Gymnura crebripunctata) helped scientists study the joints in its wings. (Photo by Adam Summers)

A passenger waits after his train arrived in Nouadhibou, Mauritania’s second largest city and the main export port for the country’s iron ore industry, on June 25, 2014. The mining company’s employees proudly call their firm the lung of their nation's economy and the train that ferries the ore to the coast stretches some two kilometres, making it one of the world's longest. SNIM mines black iron ore in the northern town of Zouerate, a remote desert location which nevertheless attracts people from all over the country looking for work. (Photo by Joe Penney/Reuters)

An African immigrant tries to jump a fence into a ferry terminal in the western Greek town of Patras April 28, 2015. Afghan, Iranian and Sudanese immigrants, living precariously in abandoned factories in Patras, southwest Greece, try to stow away on nearby ferries to Italy as they seek a better life in Europe beyond crisis-hit Greece. (Photo by Yannis Behrakis/Reuters)

Runner English Gardner poses for a portrait at the U.S. Olympic Committee Media Summit in Beverly Hills, Los Angeles, California March 8, 2016. “My musical inspiration when I'm training is usually a lot of upbeat music”, said Gardner. (Photo by Lucy Nicholson/Reuters)

A vehicle lies on a road in Adairsville. (Photo by David Goldman/Associated Press)

Marine researcher Tomasz Furmanek, 44, from Bøjarnesveien, Norway, takes stunning images while kayaking through various fjords and lakes in the Scandinavian country. During Tomasz’s free time, he works as a freelance photographer traveling around the lakes, fjords and coastal regions of the beautiful country – and capturing breathtaking photographs. Here: Hardangerfjorden, near Ullensvang. (Photo by Thomasz Furmanek/Caters News Agency)

Club-goers dance at “Morning Gloryville” at the Ministry of Sound in south London August 11, 2015. Morning dance parties with names like “Morning Gloryville” and "Daybreaker" are gathering steam in cities across the world, giving rise to a movement known as “conscious clubbing”. Its founders aim to create the energy and community of electronic dance parties with fruit smoothies and coffee instead of the drugs and alcohol more common after nightfall. (Photo by Toby Melville/Reuters)

Workers carry sacks of coffee beans at a warehouse at the Nogales farm in Jinotega, Nicaragua January 7, 2016. Soaring temperatures in Central America due to climate change are forcing farmers to pull up coffee trees and replace them with cocoa, spurring a revival in the cultivation of a crop once so essential to the region's economy. (Photo by Oswaldo Rivas/Reuters)