Part I. Integral Geometry in the Plane: 1. Convex sets in the plane; 2. Sets of points and Poisson processes in the plane; 3. Sets of lines in the plane; 4. Pairs of points and pairs of lines; 5. Sets of strips in the plane; 6. The group of motions in the plane: kinematic density; 7. Fundamental formulas of Poincaré and Blaschke; 8. Lattices of figures; Part II. General Integral Geometry: 9. Differential forms and Lie groups; 10. Density and measure in homogenous spaces; 11. The affine groups; 12. The group of motions in En; Part III. Integral Geometry in En: 13. Convex sets in En; 14. Linear subspaces, convex sets and compact manifolds; 15. The kinematic density in En; 16. Geometric and statistical applications: stereology; Part IV. Integral Geometry in Spaces of Constant Curvature: 17. Noneuclidean integral geometry; 18. Crofton's formulas and the kinematic fundamental formula in noneuclidean spaces; 19. Integral geometry and foliated spaces: trends in integral geometry.