Dehn Functions and Non-Positive Curvature -- The Isoperimetric Spectrum -- Dehn Functions of Subgroups of CAT(0) Groups -- Filling Functions -- Filling Functions -- Relationships Between Filling Functions -- Example: Nilpotent Groups -- Asymptotic Cones -- Diagrams and Groups -- Dehn’s Problems and Cayley Graphs -- Van Kampen Diagrams and Pictures -- Small Cancellation Conditions -- Isoperimetric Inequalities and Quasi-Isometries -- Free Nilpotent Groups -- Hyperbolic-by-free groups.