Abstract: Sand is a playful material, both in practice and in principle, given its complex,  and so unexpected, behavior. We address several aspects of this complexity, beginning with jamming in frictional granular packings from the perspective of rigidity percolation, or the emergence of a spanning rigid cluster. We will also discuss building frictional versus frictionless packings in the context of minimal rigidity proliferation. Finally, we will present ongoing efforts to create a physical learning system with a pile of sand, hence potentially bringing new meaning to the words “playful material”.