Gene Regulatory Networks, Volume 139 in the Current Topics in Developmental Biology series, highlights new advances in the field, with this new volume presenting interesting chapters written by an international board of authors. Topics in this release include Mouse hindbrain GRN, Xenopus endoderm GRN – organogenesis, Vertebrate limb GRN, The notochord gene regulatory network in chordate evolution: conservation and divergence from Ciona to vertebrates, Ciona early embryo GRNs, Boolean logic models, Modeling GRN response to morphogen gradient, GRN architecture, Theory of GRN evolution, Evolution of fly segmentation GRNs, GRN evolution in echinoderms, Evolution of network specificity, and more.