We study the problem of containment of shape expression schemas (ShEx) for RDF graphs. We identify a subclass of ShEx that has a natural graphical representation in the form of shape graphs and whose semantics is captured with a tractable notion of embedding of an RDF graph in a shape graph. When applied to pairs of shape graphs, an embedding is a sufficient condition for containment, and for a practical subclass of deterministic shape graphs, it is also a necessary one, thus yielding a subclass with tractable containment. Containment for general shape graphs is EXP-complete. Finally , we show that containment for arbitrary ShEx is decid-able. CCS CONCEPTS • Information systems → Graph-based database models ; Resource Description Framework (RDF); • Theory of computation → Database theory; Database interoper-ability.