Molecular genetic studies rely on well-characterized organisms that can be easily manipulated. Arabidopsis thaliana--the model system of choice for plant biologists--allows efficient analysis of plant function, combining classical genetics with molecular biology. Although the complete sequence of the Arabidopsis genome allows the rapid discovery of the molecular basis of a characterized mutant, functional characterization of the Arabidopsis genome depends on well-designed forward genetic screens, which remain a powerful strategy to identify genes that are involved in many aspects of the plant life cycle.