This chapter examines the dynamics of consumer–resource interaction, one of the fundamental building blocks of food webs. In particular, it considers how consumer–resource systems that are nonexcitable and excitable respond to changes in interaction strength. The chapter begins with a discussion of two classes of interaction-strength metrics: the first focuses on instantaneous rates of change in one species with respect to another species; the second follows the longer-term influence of the removal of (or change in) one species on the density of another focal species. Continuous consumer–resource models are then described, after which two underlying mechanisms that are behind the stabilization of consumer–resource interactions are analyzed. The chapter concludes with a review of microcosm experiments and empirical data that show consistency with the proposed consumer–resource theory.