Every year about a quarter of a million people suffer a spinal-cord injury. The consequences of such an injury can be devastating, with lifelong paralysis and economic burdens. Advances in healthcare — from stem-cell therapy and neuro-regenerative drugs to high-tech exoskeletons — can reduce pain and restore mobility.

In a neuroscience special issue this week, Naturebrings together reporting and expert opinion on efforts to apply current technologies and invent new ones to probe how the brain works. Thanks to such technologies — including those designed to map neural connections down to the level of synapses and ion channels — researchers may be on the verge of opening new vistas in understanding just as long-term programmes in the European Union and United States could together pour more than US$2 billion into the study of the brain over the next decade.

Since the first X-rays were taken more than a century ago, the ability to see inside the body has been central to the advance of medicine. Progress in precision medical imaging is gathering pace, leading to new Insights in biology, with the potential for more accurate diagnoses and improved treatments.

Transcriptional programs dictate cell identity during development. This Insight highlights recent advances in transcriptional and epigenetic regulation during development and disease, including the mechanisms behind reprogramming and DNA demethylation, the role of chromosome topology, links to metabolism and small molecule drug discovery.

From green chemistry to rare earth metal catalysts, the Nature Outlook: Chemistry Masterclassuses the 2013 Lindau Nobel Laureates Meeting as a basis to explore some of the most pressing issues in chemistry, presenting the perspectives of Nobel laureates as well as the young researchers aiming to emulate their success.

Every government and organization that funds research wants to support science that makes a difference — by opening up new academic vistas, stimulating innovation, influencing public policies or directly improving people's lives. But separating the best from the rest has never been harder. This Naturespecial issue examines, through journalism and comment, how the impact of research is traced and measured — and asks whether today's evaluation systems elevate the most influential science.

Drug resistance and the HIV pandemic have thwarted efforts to rid the world of humanity's biggest killer Mycobacterium tuberculosis. We need new types of safe drug, a practical point-of-care diagnostic and ultimately an effective vaccine if we are ever to eliminate tuberculosis. But first we need a better understanding of the underlying biology.

Climate change means the coming decades are likely to bring more frequent episodes of severe drought, with potentially devastating impact on the world's ability to feed a growing population. We therefore need a sustainable agricultural system that makes the most efficient use of water and reduces expensive and environmentally challenging inputs such as fertilizer and pesticides.

This Naturespecial issue explores the Intergovernmental Panel on Climate Change (IPCC) -- an international body of hundreds of scientists and policy experts that regularly assesses the state of knowledge about how climate is changing, what impacts that will have, and how nations can mitigate the problem. A graphical introduction chronicles the history of the IPCC and how climate science has evolved over the past 25 years. One news feature examines the latest research on rising sea levels and another profiles Ottmar Edenhofer, a leader of the IPCC's upcoming report on mitigation. In a Commentary, Elliot Diringer proposes that individual actions by nations to tackle the causes of climate change can set the stage for international action. And K. John Holmes looks at the history of large-scale environmental assessments.

Cancer is not one but many diseases, continuously evolving and different in each patient. This Insight covers key topics in cancer research, ranging from the basic understanding of tumour heterogeneity to translational research and clinical trials.

From massive open online courses (MOOCs) that are delivered to tens of thousands around the globe to adaptive digital tools that can improve outcomes by providing tailored learning experiences as well as mapping a student’s individual progress at every juncture, technology is transforming the 21st century student. Through feature articles and commentaries from experts in the field, this special collaboration between the editors of Scientific AmericanandNatureprobes the revolution underway in education and what it means for learning and research.

While survival rates for some types of leukaemia have improved dramatically, this family of blood cancers remains a potentially fatal disease. Research in epigenetics, immunotherapy, and cell transplants offers hope. And leukaemia is proving a testing ground for the theory of cancer stem cells — leading to knowledge that could advance cancer research overall.