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)

Bangladeshi fisherman feed their otters as they catch fish in Narail some 208 kms from Dhaka on March 11, 2014. The fishermen are using a rare technique that relies on coordination between man and trained otters, a centuries-old fishing partnership that has already long died out in other parts of Asia. (Photo by Munir Uz Zaman/AFP Photo)

Fireworks are seen above the Washington Monument and the White House at the conclusion of the final day of the Republican National Convention on August 27, 2020 in Washington, DC. President Donald Trump and Vice President Mike Pence accepted the nomination as the Republican candidates for a second term in the White House. (Photo by Tasos Katopodis/Getty Images)

Khadjou Sambe, 25, surfs off the coast of Ngor, Dakar, Senegal, August 18, 2020. Growing up in the coastal capital of Dakar, Sambe never saw a Black woman surfing the Atlantic swells. As Senegal's first female professional surfer, Sambe is now inspiring the next generation to defy cultural norms and take to the waves as a surfing coach for local girls. “When I am in the water I feel something extraordinary, something special in my heart”, Sambe said. (Photo by Zohra Bensemra/Reuters)

A girl poses in antlers ahead of a curfew on pub in Nottingham, a city in central England’s Midlands region on September 21, 2020 as Freshers' Week got underway. Revellers were also pictured out in Birmingham, which was plunged into a local lockdown amid a surge in coronavirus cases. (Photo by Ashley Kirk/The Sun)

New Yorkers celebrate Joe Biden winning the presidency at Washington Square Park on November 7, 2020. (Photo by Amy Lombard for NBC)

A cat sits on the empty Great Wall on February 23, 2021 in Beijing, China. Affected by the new coronavirus (COVID-19), the number of visitors to Mutianyu Great Wall in 2020 dropped by about 60%. (Photo by Lintao Zhang/Getty Images)