It is unlawful to use a pesticide in a manner inconsistent with its labeling. That single sentence — a prohibition with no counterpart in ordinary product regulation — makes the label an operative legal instrument rather than a warning, and it explains nearly everything about how this field works. This article explains what registration actually decides, why the label governs every use decision made in a field, and how the statute's preemption provision channels drift victims into trespass and nuisance claims because failure-to-warn claims are largely foreclosed. It covers applicator certification and the restricted use category, the worker protection standard, tolerances and the residue side of the regime, the endangered species consultation that has become the largest constraint on registration, and what a grower, a neighbor, or an applicator should actually do when drift occurs.