Brain-on-a-chip. Dazzling in green and magenta this image shows the nerve fibres (in green) produced by neural stem cells (in magenta) as they grow on a synthetic gel. Captured by a technique known as confocal microscopy, the image is part of research shedding light on how tinkering with the environment can affect the way in which nerve fibres grow. (Photo by Collin Edington and Iris Lee/Massachusetts Institute of Technology/Wellcome Images)

A Chinese woman wears a mask to protect from particles blown in during a sandstorm as she walks in the street on May 4, 2017 in Beijing, China. Sandstorms are common in northern China during the spring season and are caused when heavy winds from Mongolia in the north brings sand and pollutants that can blanket Chinese cities and cause air quality to deteriorate. (Photo by Kevin Frayer/Getty Images)

A Dead Leaf butterfly (Kallima inachu formosana, also called Orange Oakleaf Butterfly) rests on a tree trunk at the Taipei Zoo in Taipei, Tawian, 03 August 2019. Dead Leaf butterfly can be found in Tropical Asia from India to Japan. When its wings close, it resembles a dead leaf, providing camouflage against predators including birds, ants, spiders and wasps. (Photo by David Chang/EPA/EFE)

World's Greatest Swimming Pools: Four Seasons, Serengeti Pool, Tanzania. A show of elephants, buffalo and baboons awaits thanks to an active watering hole below the free-form infinity pool at this plush hideaway inside Serengeti National Park. Bonus: Because of infrared technology at the hole, guests can be notified on their bedroom TV when animals are approaching. When you've got word of wildlife on the horizon, catch them from your private terrace – or head back to the pool. (From $1,650). (Photo by Four Seasons)

In this Wednesday, January 23, 2019, an anti-government protester covers her face with a Venezuelan flag, and uses toothpaste around her eyes to help lessen the effect of tear gas, during clashes with security forces after a rally demanding the resignation of President Nicolas Maduro in Caracas, Venezuela. The head of Venezuela's opposition-run congress declared himself interim president at the rally, until new elections can be called. (Photo by Fernando Llano/AP Photo)

An member of the group “Pause the System” wears a face mask as she protests in front of the entrance to Downing Street in London, Friday, March 20, 2020. For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. (Photo by Frank Augstein/AP Photo)

In this Wednesday, April 15, 2020 file photo, a motorcycle delivery man rides past a billboard urging people to stay home over the coronavirus pandemic in Dubai, United Arab Emirates. Wealthier Western countries are considering how to ease lockdown restrictions and start taking gradual steps toward reviving business and daily life. But many developing countries, particularly in the Middle East and Africa, can hardly afford the luxury of any misstep. (Photo by Jon Gambrell/AP Photo/File)

Traders lay out their stools in a fishing village of Long Hai commune in Vung Tau province, Vietnam on June 17, 2020 with the market opening at midnight and trading into the early hours of the morning each day. It is the largest wholesale fishing market in the region and market traders can be seen sorting their fish into their different types before putting them into different coloured boxes for sale. (Photo by Pham Huy Trung/Solent News)