How the shape of embryos and organs emerges during development is a fundamental question that has fascinated scientists for centuries. Tissue dynamics arises from a small set of cell behaviours, including shape changes, contact remodelling, cell migration, division and extrusion. These behaviours require control over cell mechanics, namely active stresses associated with protrusive, contractile and adhesive forces, and hydrostatic pressure, as well as material properties of cells that dictate how cells respond to active stresses. In this Review, we address how cell mechanics and the associated cell behaviours are robustly organised in space and time to drive tissue morphogenesis. We first outline how not only genetic and biochemical information, but also mechanics and geometry define the time and length scales of the cell behaviours driving morphogenesis. Next, we present two idealized modes of information flow during morphogenesis. The first, akin to a program, follows deterministic rules and is hierarchical. The second follows the principles of self-organisation that rests on statistical rules, local interactions and feedback. As we review the mechanisms of four very general classes of tissue deformations, namely tissue folding and invagination, tissue flow and extension, tissue hollowing and finally tissue branching we delineate the features that fall under either of those two schemes. We suggest a conceptual framework for morphogenetic information that extends significantly from the traditional notion that genes encode shape and that encapsulates genetics and biochemistry as well as mechanics and geometry.