This month's images plumb the depths of the ocean, teeter on a vertiginous Indian 'stepwell' and soar through space.

Dumbo of the deep

Spotted in the Gulf of Mexico at the end of April by the US government’s research vessel Okeanos Explorer, this is a rarely observed ‘Dumbo octopus’ adopting a never-before-seen coiled tentacle pose. If you would like to see more of this cute member of the Grimpoteuthis genus, the vessel’s crew captured it on video. Credit: NOAA/CC by SA 2.0

Cancer in colour

This false-colour image shows yellow melanoma cells invading skin tissue, amid cyan nerve and fat cells, green muscle, and red blood vessels. To truly understand cancer spread, researchers are increasingly turning to videos of this process, as detailed in a Nature News Feature this month. Credit: Bettina Weigelin and Peter Friedl, Radboud Univ. Nijmegen

Frog fandango

Rather than sing for a lover, these frogs perform a leg-stretching ritual that serves both as a 'come-hither' dance for females and as a kung-fu kick to knock away rival males. A May paper in the Ceylon Journal of Science describes 14 new species of these loose-limbed lotharios. See Scientific American for more on these animals. Credit: S. D. Biju/Systematics Lab

Skull scan

Seven years ago, cave divers exploring the Hoyo Negro caverns in Mexico’s Yucatán Peninsula found a nearly complete skeleton of a teenager who died more than 12,000 years ago. The girl's remains were found with animal bones, including those of a sabre-toothed tiger; divers investigated the remains inside the cavern. The skeleton is now shedding light on when humans populated the Americas. See Nature’s news story for more. Credit: Paul Nicklen/National Geographic

Eyes on the Eye

This is the 40-kilometre-wide Richat Structure in Mauritania, as seen from space by Japan’s Advanced Land Observing Satellite. Erosion has sculpted what was originally a dome of rock into what is sometimes called the ‘Eye of the Sahara’. The image was taken in 2010, but was released at the start of this month. Credit: JAXA/ESA

Fantastic fins

Step into the well

This ‘stepwell’ in northwestern India is one of more than 3,000 built between ad 600 and 1850 to capture water from monsoon rains. The image comes from the documentary film Watermark, which chronicles the troubled relationship between humans and this essential substance, and is reviewed this month in Nature. Credit: Edward Burtynsky

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