The past month was an exciting time for the field of gene expression. First, Andrew Fire and Craig Mellow were awarded the Nobel Prize in Physiology or Medicine for their discovery of RNA interference (RNAi), the process by which mRNAs are targeted for destruction by specific double-stranded RNAs. Since its discovery, RNAi has become a ubiquitous technique in research laboratories and it will undoubtedly prove useful in the future for treating human diseases.

A few days later, Roger Kornberg scooped the Nobel Prize in Chemistry in honour of his work on determining the atomic structure of RNA polymerase II — insights that paved the way for an in-depth understanding of the transcriptional machinery. The contributions of Kornberg and others to the field of gene expression have recently been highlighted in the Nature Milestones in Gene Expression supplement (http://www.nature.com/milestones/geneexpression), which provides a snapshot of selected landmark papers in the field of transcription and chromatin.

Only time will tell whether the founders of the systems biology field can look forward to a future Nobel Prize. But there is little doubt that systems biology approaches have transformed biological research, as is evident from the surge in funding, research efforts and publications in this field. This month, in collaboration with our sister journal Nature Cell Biology, we present a Focus on Systems Biology: A User's Guide. This Focus aims to inform cell and molecular biologists how to apply systems biology approaches to their own research, and it can be accessed free online (http://www.nature.com/focus/systemsbiologyuserguide). In addition, print subscribers will receive a supplement containing the entire Focus content. We hope you enjoy the Focus and welcome your feedback!