Capsule habitats make it possible for human beings to survive and function in environments that would otherwise be lethal, such as space, the ocean depths, and the polar regions. The number of people entering capsules in the course of their work or for purposes of recreation is constantly increasing. However, long-term living in such habitats imposes physical and psychological risks as well as offering opportunities and benefits. This paper reviews what is known about the environmental, social, and personality aspects of adaptation to capsules, including sources of stress, selection criteria, obstacles to and facilitators of adequate coping, changes in group interaction, the role of temporal factors, and post-mission consequences.