If we were to burn NH4Cr2O7 with HgSCN in the Dark Ages in Europe and show it to anyone, it is us who would be burning next on a fiery cross of Inquisition. And it’s no wonder, since this experiment produces a truly marvelous result. At first, as you ignite the mixture of NH4Cr2O7 and HgSCN, all you can see is that it is slowly burning with a reddish flame. After a while, however, a crater is formed in the middle of the burning pile, and then, suddenly, tentacle-like appendages start sprouting from the burning mixture. And you can almost hear the scream of the mad occultist – “Come forth, Kraken! Come forth!” But of course, this is simply a chemical reaction that is called the "Pharoah's Serpent". It was also often sold in firework stores until people realized that it was toxic.

“I have been photographing this group of urban foxes in Bristol for over 12 months; what started off as a chance encounter has become an obsession for me and has changed my feelings and attitudes towards urban foxes forever...”. – Ian Wade. (Photo by Ian Wade)

“Just hanging out”. As full autumn hits the valley of Hallingdal in Norway, this bear chills out in a tree which seems to barely cover its weight. Photo location: Flå, Hallingdal, Norway. (Photo and caption by Jorgen Tharaldsen/National Geographic Photo Contest)

American rapper Belcalis Marlenis Almánzar, known professionally as Cardi B in the last decade of October 2022 says she's giving “you a*s, hair and heels”. (Photo by iamcardib/Instagram)

“Catch of the Decade”. Can you guess what happened next? Photo location: Katmai National Park, Alaska, USA. (Photo and caption by Aaron Baggenstos/National Geographic Photo Contest)

So “Anonymous Russian homeless vs PSY – GANGNAM STYLE”... In my opinion this is quite sad video (though participants obviously have contrary opinion). However it's you to judge. Video was shot somewhere on open spaces of Russia in September 2012. Enjoy if you can.

The Rio de Janeiro Olympics kick off on August 5 for some two weeks of competitive games drawing athletes as well as audiences from around the world. As they prepare to cover the event, Reuters photographers look back on their favourite pictures from past Olympics where they captured the action on the ground as well as the participants' tears and joy that followed. (Photo by Lucy Nicholson/Reuters)

“I am not a photo reporter, so I don’t feel obligated to honour every detail. What I’m trying to achieve is to emphasize the whole potential of a shot, creating a sight that I'd like if existed.. And since it’s impossible in real life, I do it in virtual :) My work is maybe more similar to ‘photo-painting’ than photography”. – Katarina Stefanović

Photo: Pannonian spring fantasy. (Photo by by Katarina Stefanović)