A woman smokes marijuana during a Global March for Marijuana in Medellin, Colombia, May 5, 2018. The annual Global Marijuana March is taking place in over 100 cities across the world in an effort to raise awareness of the benefits of medical cannabis and to call for the legalization of marijuana. (Photo by Fredy Builes/Reuters)

Ana Mendez Casteñeda smokes marijuana during “Fumaton 420” outside the national Senate in Mexico City, Tuesday, April 20, 2021. The demonstrators are calling for the legalization of marijuana. (Photo by Marco Ugarte/AP Photo)

Thick smoke rises during an eruption from Mount Merapi, Indonesia's most active volcano, as seen from Tunggularum village in Sleman on March 11, 2023. (Photo by Devi Rahman/AFP Photo)

Fire and smoke erupt from a building just after an Israeli airstrike in Beirut's southern Shayah neighbourhood on November 22, 2024, amid the ongoing war between Israel and Hezbollah. (Photo by AFP Photo/Stringer)

A general view shows smoke and volcanic ashes billowing from volcano Cotopaxi in Pedregal, Ecuador, late 07 October 2015. (Photo by Jose Jacome/EPA)

Suat Demir, a 52-year-old parter, smokes a cigarette after finishing his work day in Istanbul, Turkey, Thursday, October 2, 2025. (Photo by Emrah Gurel/AP Photo)

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)