Abstract Preimplantation development encompasses the zygote to blastocyst stages, occurring in vivo within the Fallopian tube and in vitro within embryology labs worldwide. During these first five days of life, several key morphologic changes take place facilitating cell fate specification and resulting in blastocyst assembly containing ICM and trophectoderm lineages. These include cell polarization, embryo compaction and inner-outer segregation, which transform the collection of blastomeres into a morula. Subsequently, the blastocoel cavity forms and expands followed by hatching from the zona pellucida prior to implantation. This ability to self-organize has enabled live imaging of these events within intact embryos. Moreover, this has revealed the dynamics of early mitoses, nuclear morphology and cytoskeletal changes driving early development. Although a great deal has been learned in the mouse, events in the human embryo remain relatively unknown. Recent achievements in stem cell-based embryoid models and non-invasive live imaging now poise researchers to make significant advancements unveiling human embryo development. Furthermore, a comprehensive understanding of human embryogenesis is essential to improving IVF efficiency and outcomes. Preimplantation development in mouse and human will be reviewed with a focus on recent discoveries made possible by live imaging.