We examined leaf morphology, anatomy, and margin development in wild‐type and mutant leaves in order to define the genetic pathways controlling the different stages of leaf development in tomato. Tomato mutants were placed into four categories based on the degree of leaf complexity and margin development. Mutant phenotypes ranged from little or no blade expansion (Type I mutant wiry [w]), reduced leaf complexity (Type II mutants Lanceolate [La] and entire [e]), and reduced margin complexity (Type III mutants solanifolia [sf], trifoliate2 [tf2], and potato leaf [c]) to excessive leaf complexity (Type IV mutants Mouse ears [Me], Curl [Cu], clausa [clau], and complicata [com]). Based on our analyses, we conclude that the central domain of the terminal leaflet is established first, followed by blade expansion and further partitioning of the blade into a proximal domain that will promote the initiation of lobes and lateral leaflets. The mutant w causes a defect in blade expansion, La inhibits the establishment...