Syrian refugees sit behind barbed wire as they wait to cross into Macedonia at the Greek-Macedonian border, near the village of Idomeni, August 21, 2015. (Photo by Yannis Behrakis/Reuters)

A model presents the Flesby, a one-seater mobility concept car, during a media preview of the 45th Tokyo Motor Show in Tokyo, Japan on October 25, 2017. Japan's flagship automakers present their futuristic visions for the post-fossil fuel era at the Tokyo Motor Show that kicks off Wednesday. (Photo by Kim Kyung-Hoon/Reuters)

Veteran cholita wrestler Jennifer dos Caras, 45, holds a cement block over teen wrestler Lucero la Bonita in the ring in El Alto, Bolivia, Monday, January 21, 2019. Trainees of cholita wrestling are still a year away from their full professional debuts while competing in matches against established athletes. (Photo by Juan Karita/AP Photo)

A horse smiles at the camera. See the beautiful images of horses gleefully playing in Iceland mountain ranges. The horses have been spotted smiling and cuddling in remote locations across the nation. (Photo by Bragi J. Ingibergsson/Caters News)

Soap Bubble Structures by Kym Cox. Bubbles optimise space and minimise their surface area for a given volume of air. This phenomenon makes them a useful tool in many areas of research, in particular, materials science and “packing” – how things fit together. Bubble walls drain under gravity, thin at the top, thick at the bottom, which interferes with travelling lightwaves to create bands of colour. Black spots show the wall is too thin for interference colours, indicating the bubble is about to burst. (Photo by Kym Cox/2019 Science Photographer of the Year/RPS)

This 2014 series Shanghai Tian Wa saw Chinese photographer Liu Tao train his lens on two distinct districts in Shanghai. Here: “Shanghai Tian Wai №26, 2014”. (Photo by Liu Tao/The Guardian)