Leaf shape is mutable, changing in ways modulated by both development and environment within genotypes. A complete model of leaf phenotype would incorporate the changes in leaf shape during juvenile-to-adult phase transitions and the ontogeny of each leaf. Here, we provide a morphometric description of >33,000 leaflets from a set of tomato (Solanum spp) introgression lines grown under controlled environment conditions. We first compare the shape of these leaves, arising during vegetative development, with >11,000 previously published leaflets from a field setting and >11,000 leaflets from wild tomato relatives. We then quantify the changes in shape, across ontogeny, for successive leaves in the heteroblastic series. Using principal component analysis, we then separate genetic effects modulating (1) the overall shape of all leaves versus (2) the shape of specific leaves in the series, finding the former more heritable than the latter and comparing quantitative trait loci regulating each. Our results demonstrate that phenotype is highly contextual and that unbiased assessments of phenotype, for quantitative genetic or other purposes, would ideally sample the many developmental and environmental factors that modulate it. tpc130112_SupplementalDS1Supplemental Dataset 1: Morphometric traits for >55,000 leaflets analyzed in this study. For each leaflet, the corresponding file name (“file”), experiment from which it is derived (“experiment”), genotype (“genotype”), leaf number if applicable (“leaf”), leaflet type (“leaflet_type”, where “t” = terminal leaflet, “a” = left distal lateral leaflet, “b” = right distal lateral leaflet, “c” = left proximal lateral leaflet, “d” = right proximal lateral leaflet), proximal-distal position (“prox_dist”), age of the plant sampled (“age”, which is measured as leaf plus flower number for the chamber experiment and leaf number for the wild species experiment), whether the leaflet is on the left or right side of the leaf (“left_right”), light treatment (“trt”, where “l” = low red-to-far red, or simulated foliar shade, and “h” = high red-to-far red, or simulated sun), and trait values for circularity (“circ”), aspect ratio (“ar”), roundness (“round”), solidity (“solid”), allPCs, and asymPCs are given.tpc130112_SupplementalDS2Supplemental Dataset 2: Heteroblasty and experimental design information for S. lycopersicum, S. pennellii, and IL leaflets measured in the chamber experiment. For each leaflet is provided the corresponding image file name (“file”), the trait for which hPCs and other information is calculated (“trait”), the mean value of the trait for the plant across the leaflets considered (“mean”), the value of the trait for specific leaflets (terminal leaflet 1, “lft_1t”; mean distal lateral leaflets 2, “lft_2ab”; terminal leaflet 2, “lft_2t”; mean distal lateral leaflets 3, “lft_3ab”; terminal leaflet 3, “lft_3t”; mean distal lateral leaflets 4, “lft_4ab”; terminal leaflet 4, “lft_4t”), hPC values, replicate (“rep”), light treatment (“trt”, where “H” = simulated foliar shade, “U” = simulated sun), shelf (“shelf”), tray (“tray”), tray position (“position”), IL genotype (“geno”), species or IL information (“species”), the number of leaves and leaf primordia at the time of harvest (“lfn”), the number of flower and floral primordia at the time of harvest (“flwrn”), and the leaf plus flower number (“lf.flow.number”).tpc130112_SupplementalDS3Supplemental Dataset 3: hPC variance values. The fraction of shape variance in leaflets across the heteroblastic series explained by hPCs for each shape attribute is provided.tpc130112_SupplementalDS4Supplemental Dataset 4: Loading values for cfPCA. Provided are the loading values of different traits for cfPCs. See text for details.