Particulate materials are fascinating systems. They span a variety of scales, both in time and space, from colloidal suspensions to geophysical flows and planetary bodies. It seems difficult at first sight to embrace a flock of birds, a culinary emulsion and a pile of construction materials into common models. Yet, such seemingly disparate systems share common features. Encompassing them into a uniting framework represents a captivating physics problem, an important engineering challenge, and an essential step for humans' progress.