These adorable cats – which are twins – showcase their contrasting blue and green eyes. The cats have a condition called heterochromia iridis, which causes each eye to vary in color. (Photo by @sis.twins/Caters News Agency)

Van cats, relatively large, have a chalky white coat, sometimes with ruddy coloration on the head and hindquarters, and have blue or amber eyes or have heterochromia, are seen at “Cat Villa”, established to protect the cats in Van, Turkey on January 20, 2021. Internationally valid “health certificate” is prepared for Van cats, visited by local and foreign tourists, within a project to protect their generations and increasing their numbers. Health certificates with information such as name, breed, gender, eye color, date of birth, tail feature, color, hearing status and identity are given to people who want to adopt cats. (Photo by Mesut Varol/Anadolu Agency via 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)

There is an endless bounty of eye-catching gemstones throughout the world and this spectacular boulder opal is one unique beauty that looks like a shimmering crystal encased in a tree fossil. Its opalescent sheen seeps through the cracks of the seemingly wooden rings in lustrous hues of emerald green and aqua blue. Like something out of a fairy tale, the triangular piece radiates through an organic pattern mimicking the growth rings of tree.

Three samurai warriors in armour, circa 1880. (Photo by Kusakabe Kimbei). P.S. All pictures are presented in high resolution.

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)

“In a nutshell and to prevent my english readers from experiencing eye bleeding after having read too many syntax errors, I’m a french journalist – I work as an editor, not as photographer – who happens to be nuts about photography. Being the happy owner of too many Leica M for a man to shoot, I spend most of my free time shooting my friend and my town, Strasbourg, in b&w and sometimes in colors”. – Manuel Plantin

Photo: “Even detectives got the blues”. Strasbourg, 2011 (Photo by Manuel Plantin)

Shimmering clearest blue and stretching as far as the eye can see, this is one of Iceland's famed crystal ice caves. The giant solid waves look frozen in time but they are slowly moving along as part of the Vatnajokull Glacier – which stretches across eight per cent of the island. The images were captured in February 2014 by British photographer Rob Lott, 49. Photo: A wide view of Rob Lott in the crystal ice cave in the Vatnajokull Glacier, Iceland. (Photo by Rob Lott/Barcroft Media)