A woman wears a face mask in the part of the city near neighbourhoods known for burning coal for heating in Ulaanbaatar, Mongolia January 26, 2017. Not many people in Ulaanbaatar wear masks to protect themselves against pollution. (Photo by B. Rentsendorj/Reuters)

With its huge eyes, comical name and diminutive size, Mark R. Smith’s image of a baby Hawaiian bobtail squid can’t help but raise a smile. A curiously endearing creature, the cephalopod is just 1.5cm across, its mantle cavity bearing more than a passing resemblance to a rather natty shower cap. But it is also a beautiful example of symbiosis – nature’s version of “I’ll scratch your back if you scratch mine” – for on the underside of the squid is a light organ which houses bioluminescent bacteria. The squid offers the bacteria protection and food, while the bacteria emit a glow – a handy trait that the squid uses to offset its silhouette, helping it to evade predators in the depths below. Mark R. Smith’s entry combines several images of a Hawaiian bobtail squid with different focus lengths to create a final picture with greater depth of field than normal. (Photo by Mark R. Smith/Wellcome Images/Macroscopic Solutions)

A suspected Vietcong is kicked by a Vietnamese soldier holding a rifle as another soldier attempts to tie his hands on October 22, 1965. The prisoner was one of 15 captured October 21 near Xom Chua when government troops raided in the plain of reeds area. Troops killed 43 suspected Vietcong and seized some arms. (Photo by Richard Merron/AP Photo)

Russian cosmonaut Alexander Skvortsov, Expedition 40 flight engineer, attired in a Russian Orlan spacesuit, participates in a session of extravehicular activity (EVA) in support of science and maintenance on the International Space Station on August 18, 2014. During the five-hour, 11-minute spacewalk, Skvortsov and cosmonaut Oleg Artemyev (out of frame) deployed a small science satellite, retrieved and installed experiment packages and inspected components on the exterior of the orbital laboratory. (Photo by NASA)

Coaches of the North-East Express passenger train that derailed late Wednesday near Raghunathpur railroad station in Buxar district of Bihar state, India, Thursday, October 12, 2023. The train was on its way to Assam state from New Delhi. (Photo by Aftab Alam Siddiqui/AP Photo)

A surfer dressed as Santa Claus participates in the 16th annual “Surfing Santas” event on Christmas Eve in Cocoa Beach, Florida, December 24, 2024. (Photo by Giorgio Viera/AFP Photo)

A kingfisher plunged into the water in Trowbridge, Wiltshire, UK in the first decade of June 2025, to grab a fish for lunch – but its prey twisted free in a last-second escape. (Photo by Alan Benson/Caters News Agency)

Broomfield Samson, a rare breed Suffolk punch, and his rider, Alison Carroll, cool off in the River Lune at Loyne Bridge near Gressingham in Lancashire, UK on May 21, 2024. (Photo by James Glossop/ The Times & Sunday Times)