Since its foundation over 50 years ago by George Batchelor, the Journal of Fluid Mechanics has published theoretical, computational and experimental investigations on all aspects of the mechanics of fluids. Over this time, the research community of talented scientists, engineers and mathematicians contributing to the astonishing development of our understanding of fluid flow has grown enormously. This growth has naturally been reflected in the growth of the Journal. In 1956 there were 39 papers published in a single volume of 672 pages, while in 2008 there were 450 papers, extending over nearly 11000 pages and 24 volumes. The array of topics considered has similarly broadened hugely, as a quick scan of the titles of the papers can verify. Building on traditional fields such as aerodynamics, geophysical flows and wave phenomena, research into fluid dynamics has spread into new and exciting areas such as biological flow, granular media, and flows on extremely small physical and time scales.