To shed light on the making of plant leaves, in 1993 we began an undertaking to identify as many Arabidopsis viable and fertile mutants with abnormal leaf morphology as possible. We identified 28 fast-neutron- and 153 ethyl-methane sulfonate-induced mutations, which fell into 8 and 94 complementation groups, respectively (Berná et al., 1999). We also studied 115 publicly available mutant lines isolated by previous authors (the Arabidopsis Information Service [AIS] collection), which fell into 47 complementation groups (Serrano-Cartagena et al., 1999). In a complementary approach, we also analyzed leaf architecture in 166 natural wild-type accessions and two populations of recombinant inbred lines (Candela et al., 1999; Pérez-Pérez et al., 2002; Juenger et al., 2005). Our mutants are freely available on request.