Montessori education was developed over 100 years ago, and persists as a marginal 'niche reform' of the standard model. Here I discuss two unresolved dichotomies in early childhood education -- the tension between work and play, and between structure and freedom. I explain how Montessori collapses and thereby resolves the dichotomies, and does so in a contemporary theoretical frame -- one that is dynamical rather than linear. I next describe the origins and functioning of Montessori preschool environments, outcomes from the most methodologically sound studies to date, and impediments to Montessori's more widespread adoption. I also show how Montessori is a culturally responsive pedagogy, and conclude by return to the dichotomies and how Montessori makes sense for the modern era.