Extraembryonic tissue spreading in the scuttle fly Megaselia abdita requires mechanical decoupling from the underlying yolk sac.

Evolutionary reduction in tissue number involves the simplification of the seaming process but not signaling during epithelial fusion.

Quantitative system-level analysis of a pattern-forming gene regulatory network in a non-model organism shows that dynamic changes in gene expression evolve through quantitative system drift.

BMP guides the evolution of extraembryonic tissue complexity in fly embryos through changes in the control of a positive feedback circuit.

Functional recapitulation of a likely evolutionary gain in gene expression shows that two genes are sufficient to switch mesoderm cell internalization from stochastic cell ingression to coordinated epithelial invagination.

Dissection of a cis-regulatory element (CRM) in its native chromosomal context using CRISPR/Cas9 editing and novel 'Active Genetics' reveals new features of CRM function and insights into how such regulatory elements change during evolution.