The Sun’s outer atmosphere is much hotter than the surface, reaching more than a million kelvin, but how sufficient energy is transferred and dissipated has remained a puzzle. Recent advances in high-resolution imaging of small-scale structures on the solar surface (from the Swedish 1-m Solar Telescope) revealed swirling events in the Sun’s chromosphere, the atmospheric layer sandwiched between the corona and the photosphere. This paper reports observations from NASA’s Solar Dynamics Observatory spacecraft that reveal rapidly rotating magnetic structures in the transition region and low corona that are associated with these chromospheric swirls. These structures, resembling super-tornadoes under solar conditions, reach from the convection zone into the upper solar atmosphere and provide an alternative mechanism for channelling energy from the lower to the upper solar atmosphere  a possible explanation for the heating of the outer solar atmosphere that results in the observed temperatures. The cover shows a visualization (using VAPOR software) of a computer simulation (using CO5BOLD) of a swirling magnetic ‘tornado connecting the observed surface of the Sun with the outer atmosphere.

A rock-art representation of domesticated cattle is between 5,000 and 8,000 years old, from the Wadi Imha in the Tadrart Acacus Mountains of the Libyan Sahara. Similar images - some of which even include scenes of milking - are widely distributed in the region and suggest that cattle played a big part in the lives of ancient humans in the 'Green' Sahara during the Holocene. Rock art is notoriously difficult to date. However, using isotope analysis of absorbed food residues in pottery excavated from the Takarkori rock shelter in the Libyan Sahara by the Archaeological Mission of the Sapienza University of Rome, Julie Dunne and colleagues report the first unequivocal chemical evidence of dairying in the archaeological record, in prehistoric Africa in the fifth millennium BC. These findings confirm that domesticated cattle, and a dairying economy, were part of early Saharan pastoralism. (Photo: Roberto Ceccacci, Sapienza Univ.)

The cover illustration is inspired by the original painting Our Self-Portrait: the Human Microbiome by scientific artist Joana Ricou (http://go.nature.com/xrdb9o). The Human Microbiome Project (HMP), supported by the National Institutes of Health Common Fund, has the goal of characterizing the microbial communities that inhabit and interact with the human body in sickness and in health. In two Articles in this issue of Nature, the HMP Consortium presents the first population-scale details of the organismal and functional composition of the microbiota across five main body areas. An associated News & Views discusses these initial results  which, along with those of a series of co-publications, already constitute the most extensive catalogue of organisms and genes related to the human microbiome yet published  and highlights some of the major questions that the project will tackle in the next few years. (Cover graphics: Steven H. Lee/ Studio Graphiko.)

Earth is getting a second chance. At the 1992 Rio Earth Summit, the world’s leaders pledged to protect the planet’s climate and biodiversity. Since then, however, the situation has deteriorated further. Twenty years on, on the eve of the second Rio Earth Summit, we report on what went wrong  and how things may yet be put right. Elsewhere in the issue, a series of Reviews and research papers explores how biodiversity loss is affecting ecosystems, and how much the consumption patterns of the developed world are to blame. Cover by Julene Harrison (photo: Samuel Acosta/Shutterstock).