Two boys look out from the Mangueira slum towards the Maracana Stadium that is hosting the Rio's 2016 Summer Olympics opening ceremonies, in Rio de Janeiro, Brazil, Friday, August 5, 2016. (Photo by Leo Correa/AP Photo)

Wrestlers perform at an all female wrestling event in London. England on August 17, 2017. (Photo by Neil Hall/Reuters)

A gory fight to the death between snarling dogs and captured wild boars. Gathered around a bamboo-walled arena, Indonesians in this remote part of Java island seem eager to watch the blood-curdling contests, known locally as “adu bagong” (boar fighting). Not surprisingly, animal rights activists are up in arms against the regular spectacle, which began in the 1960s when wild pig numbers in this area in West Java soared and they were hunted to protect crops. Here: Women share a joke as they walk to a paddy field in Cikawao village of Majalaya, West Java province, Indonesia, October 12, 2017. (Photo by Reuters/Beawiharta)

A thirsty timber wolf, Lithuania, 2018. (Photo by Erikas Plucas/Alamy Stock Photo)

Most people know Nikon as a purveyor of pro and consumer-grade digital cameras. But the company's expertise with optics bleeds over into related markets – it's one of the science community's major suppliers of microscopes. And each year the company asks the community to send it some of their favorite images of tiny objects. A panel of scientists and journalists have chosen the best of this past year's submissions, which Nikon has placed on its Small World site.

Photo: Honorable Mention. “Snow crystal, illuminated with colored lights (5x)”. (Photo by Dr. Kenneth Libbrecht, California Institute of Technology (Caltech), Department of Physics, Pasadena, California, USA)

“Einar Erici (1885–1965) was a physician by profession, working at a tuberculosis hospital in Stockholm, even running a private medical practice. He was by then the most renowned Swedish expert of church organs and organ builders, and his archival collection is today held by the Swedish National Heritage Board. This archive includes mostly writings, such as letters and manuscripts for published articles and essays, but also more than 2 000 black and white photos – original prints, glass plates and film negatives”. – Swedish National Heritage Board

Photo: Priest, Valamo Monastery, Karelia, Russia (then Finland), 1930s. Father Venerius with a birchbark basket. (Photo by Einar Erici)

Gardener Peter Glazebrook poses for photographers with his world record breaking onion at The Harrogate Autumn Flower Show on September 16, 2011 in Harrogate, England. Peter Glazebrook from Newark, Nottinghamshire claimed a Guinness World Record with his giant onion weighing 8.150 kg. (Photo by Christopher Furlong/Getty Images)

Soldiers, including two recruits who have brought some chickens, at Victoria prepare to board the train for the battle front. (Photo by Hulton Archive/Getty Images)