Seed dormancy has been studied intensely over the past decades and, at present, knowledge of this plant trait is at the forefront of plant biology. The main model species is Arabidopsis thaliana, an annual weed, possessing nondeep physiological dormancy. This overview presents the state-of-the-art of seed dormancy research, focusing mainly on physiological and molecular-genetic aspects in this species. It has become clear that, like in many other organisms, the dormancy and stress responses are tightly associated in seeds. The plant hormones abscisic acid and gibberellins play a pivotal role in the acquisition of developmental arrest or repression of metabolic inactivity, respectively. Some attention is given to the overlapping dormancy and stress responses, commonly studied in many other organisms but only marginally in seeds.