Delivering genes or RNAs to cells and tissues, or correcting existing genes, is an approach with great potential to treat a range of diseases. Since its inception about 20 years ago, the field of gene-based therapies has met with considerable challenges and controversy. However, recent progress has helped to realize the initial promise of these approaches and several gene-based therapies have now achieved success in clinical trials.

The pace of stem cell research continues to accelerate, with rapid advances being made in diverse areas, from understanding the fundamentals of their biology to how these unique cells can give insights into the genetic and cellular causes of human disease. This joint Focus between Nature Cell BiologyandNature Reviews Geneticsreviews the latest developments, including the nature of pluripotency, methods for manipulating cell fate and how stem cells might be used in clinical and research applications.

Influenza pandemics occur with some frequency, as indicated by the recent outbreak of swine flu (influenza A (H1N1)). Learn more about influenza, previous 'flu pandemics, preventative measures against 'flu and how the spread of disease can be modelled and possibly predicted with these selected Nature Reviews MicrobiologyandNature Reviews Geneticsarticles.

At the point when theory is about to be translated into practice in genomic medicine, this collection of Perspective articles describes human genome variation studies taking place in Mexico, India, Thailand, and South Africa. This Supplement discusses the challenges and opportunities facing these and other countries in the developing world as they begin to harness genomics for the benefit of their populations.

A number of pressing, interrelated, global challenges face the human race in the 21st century: environmental change, population growth and a rapid decline in fossil fuel reserves. This Focus issue looks at ways in which genetics can be harnessed to address these problems, from crop genetic engineering for improved yields and economical biofuel production, to the genetic monitoring of effects of environmental change on the world's biodiversity.

MicroRNAs (miRNAs) — an abundant class of small non–protein–coding regulators of gene expression — play an important role in tumorigenesis and, depending on their targets, can function as tumour suppressors or oncogenes. Crucially, miRNA–expression profiling of human tumours has identified signatures associated with diagnosis, staging, progression, prognosis and response to treatment.

In the past 2 years genome-wide association studies in humans have revealed dozens of disease-associated loci and have provided insights into the allelic architecture of complex traits. Along the way, much has been learned about how best to carry out such studies. The articles in this series examine these design issues and the technical challenges that remain; for example, identifying association signals and interpreting the molecular mechanisms by which they exert their biological functions.

Evolutionary developmental biology (evo–devo) attempts to integrate an understanding of developmental processes into the Modern Synthesis of genetics and evolution, which classically focused on how allele frequencies changed in populations. The web focus contains articles that look at the conceptual advances that evo–devo is offering to evolutionary biology as a whole, as well as articles that describe specific experimental evo–devo studies.

Milestones in DNA Technologies is a collaborative project involving three journals - Nature,Nature MethodsandNature Reviews Genetics- and celebrates more than half a century of discoveries and applications of DNA technologies.

Nature Reviews presents a Collection on microRNAs, which includes Reviews from Nature Reviews Genetics,Nature Reviews CancerandNature Reviews Molecular Cell Biology. The articles have been specially selected to provide an introduction to diverse aspects of microRNA biology, including their biogenesis, function in normal development and cancer, and evolutionary implications of their impact on gene regulation.

The fundamental roles of epigenetics in genome regulation make an understanding of mechanisms such as DNA methylation and histone modification an essential goal, both for basic and applied research. The topics covered in this web focus range from basic research in chromosome biology and gene regulation, to stem cell research, environmental epigenetic and cancer epigenomics, where exploring the role of epigenetics has the potential to lead to clinical advances.

Fields as disparate as population genetics, systems biology, mathematical modelling of development and transcription profiling rely on quantitative descriptions, and statistical analysis — once a concept foreign to mainstream genetics — is pervading every aspect of the field. The articles in this Focus untangle the complex issues in statistical analysis, and present the continually debated solutions and the authors' opinion on future trends.