"There is a long-running controversy about how early cell fate decisions are made in the developing mammalian embryo. In particular, it is controversial when the first events that can predict the establishment of the pluripotent and extra-embryonic lineages in the blastocyst occur. It has long been proposed that the position and polarity of cells at the 16- to 32-cell stage embryo influence their decision to either give rise to the pluripotent cell lineage that eventually contributes to the inner cell mass (ICM), comprising the primitive endoderm (PE) and the epiblast (EPI), or the extra-embryonic trophectoderm (TE) surrounding the blastocoel. The positioning of cells in the embryo at this developmental stage could be largely the result of random events, making this a stochastic model of cell lineage allocation. Contrary to such a stochastic model, some studies have detected putative differences in the lineage potential of individual blastomeres before compaction, indicating that the first cell fate decisions may occur as early as at the 4-cell stage. Using a non-invasive, quantitative in vivo imaging assay to study the kinetic behavior of Oct4, a key transcription factor (TF) controlling pre-implantation development in the mouseembryo, we identified Oct4 kinetics as a predictive measure of cell lineage patterning in the early mouse embryo. Here, we will investigate the molecular nature of this kinetic behavior that controls the development of the first specialized cells in living mouse embryos. Building upon our previous results we will test the hypothesis that TF kinetic behaviors may represent a general mechanism to establish heterogeneities and control lineage patterning in the mouse embryo by systematically measuring the kinetic parameters of the main TFs essential for pre-implantation development. We will further determine if TF kinetics are a unique mark that defines the pluripotent state by comparing TF kinetics in the embryo to embryonic stem cells."