Following fertilization, gametes undergo epigenetic reprogramming in order to revert to a totipotent state. How embryonic cells subsequently acquire their fate and the role of chromatin dynamics in this process are unknown. Genetic and experimental embryology approaches have identified some of the players and morphological changes that are involved in early mammalian development, but the exact events underlying cell fate allocation in single embryonic cells have remained elusive. Experimental and technological advances have recently provided novel insights into chromatin dynamics and nuclear architecture in single cells; these insights have reshaped our understanding of the mechanisms underlying cell fate allocation and plasticity in early mammalian development.