The adhesion and removal of particles to and from substrates is a topic of great interest for both scientific and technological reasons. When a particle contacts a substrate, the adhesion-induced stresses cause deformations of the materials, which, in turn, affect adhesion. The size and nature of these deformations depend on both the interaction potential and mechanical properties, such as their elastic moduli and yield strengths of the contacting materials. Because of the number of interacting factors, particle adhesion and removal is a complex topic. Much of the present understanding of particle adhesion is based on the theoretical work of Johnson, Kendall, and Roberts, Dejaguin, Muller, and Toporov, and Maugis and Pollock, augmented by systematic experimentation. This paper will review the current understanding of particle adhesion and will illustrate effects of the particle-substrate interface using scanning electron micrographs.