Over the past two decades, our understanding of mouse development from implantation to gastrulation has grown exponentially with an upsurge of genetic, molecular, cellular, and morphogenetic information. New discoveries have exalted the role of extraembryonic tissues in orchestrating embryonic patterning and axial specification. At the same time, the identification of unexpected morphogenetic processes occurring during mouse gastrulation has challenged established dogmas and brought new insights into the mechanisms driving germ layer formation. In this article, we summarize the key findings that have reinvigorated the contemporary view of early postimplantation mammalian development.