We present a concise summary of embryonic development in hagfish and lampreys. With the rise of evolutionary developmental approaches, the rapidly advancing frontier of research on these jawless vertebrates has revealed a number of developmental traits common among cyclostomes (e.g., distribution of trigeminal neural crest cells) and even vertebrates (e.g., brain regionalization), as well as an array of lineage-specific features (e.g., sclerotome differentiations, shift of branchial pouches). In addition to the wealth of data on gene expression patterns, techniques such as reporter expression assay, cell labeling, and functional analysis using morpholino and CRISPR are beginning to identify patterns and mechanisms of tissue inductions and interactions underlying the cyclostome body plan. However, it remains challenging to trace developmental traits to a common ancestry because each of the three living vertebrate lineages (hagfish, lampreys, gnathostomes) and their invertebrate outgroups sits atop a long branch. Fossils and embryos can complement each other to reinforce inferences about stem conditions and, with recent advances, such a reciprocal approach may be within our reach.