A visitor takes pictures with a smartphone of an artwork entitled “Blue Europe, 2015” by Chinese artist Liu Bolin, on display during the exhibition “Visible Invisible” at the Mudec Museum in Milan on May 14, 2019. Liu Bolin known as “the invisible man” for his photographic self-portraits, focused on a body-painting blending with the surrounding area. (Photo by Miguel Medina/AFP Photo)

When Dutch photographer Marcel Heijnen moved to Hong Kong, the territory’s shop cats instantly caught his eye. While the “feline emperors” are the stars, his shots also offer insights into Hong Kong’s wares, from dried fish to paper. Here: Hong Kong Shop Cats #17. (Photo by Marcel Heijnen/Blue Lotus)

A DC-10 air tanker delivers flame retardant to the Blue Cut fire in Wrightwood, Calif., Wednesday, August 17, 2016. A wildfire with a ferocity never seen before by veteran California firefighters raced up and down canyon hillsides, instantly engulfing homes and forcing thousands of people to flee, some running for their lives just ahead of the flames. (Photo by Alex Gallardo/AP Photo)

A woman uses a phone to take a “selfie” photo with cat as she stands along the barbed wire fence demarcating the “blue line” – drawn by the United Nations to mark Israel's withdrawal from southern Lebanon in 2000 – while an Israeli Merkava battle tank is deployed nearby, at a position along the border near the village of Kfar Shuba in southern Lebanon on June 11, 2023. (Photo by Mahmoud Zayyat/AFP Photo)

Pedestrians cover their face as they walk along the dusty road in Kathmandu, Nepal February 27, 2017. Nepal has forced 2,500 old vehicles off roads in its capital city of Kathmandu, part of a fight against alarming air pollution levels that have hit nine times World Health Organisation (WHO) limits. Air pollution has been a chronic problem in rapidly growing Kathmandu, which sits in a Himalayan valley and is home to more than 3mn people. (Photo by Navesh Chitrakar/Reuters)

Visitors enjoy watching the Blue Nemophila flowers bloom during the Golden Week holidays, at Hitachinaka Kaihin Park on May 02, 2010 in Hitachinaka, Ibaraki, Japan. Millions of nemophilas blossom across the “Miharashi No Oka” hill at Hitachi Seaside Park for the annual “Nemophila Harmony” flower festival. (Photo by Koichi Kamoshida/Getty Images)

“The Red-eyed Treefrog (Agalychnis callidryas) is an arboreal hylid native to Neotropical rainforests in Central America. Red-eyed tree frogs, as their name states, have red eyes with vertically narrowed noses, a vibrant green body with yellow and blue vertically striped sides, and orange or yellow webbed feet and toes”. – Wikipedia. (Photo by Donald Quintana)

Ngorongoro Crater (Tanzania). At 610m deep and 260 sq km, this is the largest unflooded caldera in the world. A blue-green vision from above it's a haven for engangered wildlife and Maasai livestock. The crater was formed three million years ago when a giant volcano, which could have been as high as Kilimanjaro, exploded and collapsed. The caldera formed the concentric fractures in the crust cracked down to a magma reservoir deep underground. (Photo by John Bryant/Getty Images)