Euphorbia peplus is an ideal plant species to develop as a model system in many ways: it is diploid, has a small genome, self-fertilizes, goes from seed to seed in less than two months, and is around 30 cm tall at maturity. To develop this species as a model system, we produced a high-quality chromosome-level genome assembly and annotation. We then used these genomic resources to interrogate several biological questions. First we investigated Euphorbiaceae genome evolution, asking why this family has such variable chromosome size and number. We found that a lack of Ty3 transposons accounted for E. peplus’s small genome size, and chromosomal fragmentation and rearrangement rather than chromosome duplication and diploidization accounted for the shifts in chromosome number that we observed between Euphorbiaceae species. We also found that putative biosynthetic genes for ingenol mebutate, a diterpenoid of medical value, were located together in a genetic cluster, or metabolon. Then we investigated the evolutionary origin of the Euphorbia reproductive structure, the cyathium. The cyathium has been interpreted by most sources as an inflorescence but has also been interpreted as a complete flower. We assessed transcriptional patterns of ABCDE genes, the whorls’ gene ontology and transcriptomic similarity to Arabidopsis whorls, and sequence evolution in key floral genes. Our data supported the cyathium as an inflorescence, not a complete flower. Finally, we wanted to use the E. peplus genome to investigate the development of laticifers, the cells that contain latex. Working with a collaborator, we characterized E. peplus mutants lacking laticifers in their leaves and stems. We also used micro-X-ray-fluorescence from a synchrotron source to characterize the localization of zinc, and found that zinc is concentrated in E. peplus laticifers in vivo. Overall, E. peplus is a promising model system for developmental features unique to Euphorbia and the Euphorbiaceae such as cyathia and laticifer cells.