Book excerpt: The 45 papers presented in this volume all share the common goal of constructing continuum models based on the micro behaviours of granular materials. Computer simulations continue to provide observations to aid modelling, while new experimental works begin to show promise for increased understanding in this area. Theoretical studies have extended into transitions between the rapid and quasi-static regimes and the fluid and solid mixture flows. Exciting new topics discussed in this volume include: concepts of a measure for randomness in quasi-static granular materials, which is analogous to the granular temperature in a rapid flow; scaling effects in granular media and their implications in both physical and computer simulations; instability; and boundary effects on heterogeneous behavior in simple flow configurations, which are posing new challenges for mathematical modelling. The volume will prove indispensable reading for researchers interested in the current developments in the fundamental aspects of mechanics of granular materials.