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)

A Spanish national police officer uses his club to hit a protester during a demonstration called the Catalan pro-independence left youth group “Arran” on October 19, 2019 in Barcelona, a day after nearly 200 people were hurt in another night of violent clashes in Catalonia. The deterioration came on the fifth consecutive day of protests in the Catalan capital and elsewhere over a Spanish court's jailing of nine separatist leaders on sedition charges over a failed independence bid two years ago. (Photo by Josep Lago/AFP Photo)

Rowers enter in Canaregio river during the 42nd Venice Vogalonga on May 15, 2016 in Venice, Italy. 42 years ago a group of Venetians, both amateur and professional rowers, came up with an idea of non-competitive race in which any kind of rowing boat can take part. The first Vogalonga began with the message to protest against the growing use of powerboats in Venice and the swell damage they do to the historic city. (Photo by Awakening/Getty Images)

In this May 14, 2016 photo, children wearing their school backpacks climb on a cliff using a bamboo ladder on their way home from school in Zhaojue county, southwest China's Sichuan province. A village in China's mountainous west where schoolchildren must climb an 800-meter (2,625-foot)-high bamboo ladder secured to a sheer cliff face may get a set of steel stairs to improve it's safety. (Photo by Chinatopix via AP Photo)

Alejandra Guajardo, Miss Universe El Salvador 2022 poses on stage in an outfit inspired by the country's use of Bitcoin, and previously the colón and cocoa beans as a currency, during the 71st Miss Universe National Costume Show at the Ernst N. Morial Convention Center in New Orleans, Louisiana, U.S. January 11, 2023. (Photo by Benjamin Askinas/©IMG Universe LLC/Handout via Reuters)

The “voodoo” wrestler known as Panthère utters incantations above the alter of his shrine in Kinshasa, Democratic Republic of Congo, on July 27, 2023. In the capital of DR Congo, dozens of men and women – including former wrestlers – practice “voodoo wrestling”, using traditional fetishes and animals. Fights are organised in some of the city's poorest and most densely populated districts. (Photo by Alexis Huguet/AFP Photo)

In this photo provided by the Florida Keys News Bureau, Maddie Miller, of Tampa, Fla., raises her head during the World Famous Key Lime Pie Eating Championship Tuesday, July 4, 2023, in Key West, Fla. The gooey competition, whose entrants are forbidden to use their hands, has become a subtropical alternative to Nathan's Famous Fourth of July hot dog eating contest in New York City. (Photo by Rob O'Neal/Florida Keys News Bureau via AP Photo)

Girls in red neckerchiefs dance on Red Square, with the GUM, the State Department Store and the Historical Museum in the background, during a ceremony to celebrate joining the Pioneers organization and 100th anniversary of the All-Union Pioneer Organization, in Moscow, Russia, Sunday, May 22, 2022. Pro-Communist Russians are trying to preserve the Young Pioneers, which used to be the Communist league for pre-teens in the Soviet Union. (Photo by AP Photo/Stringer)