How can one describe the appearance of space and time? This chapter reviews the no-boundary proposal, which allows for a concrete calculation of the nucleation of space and time from nothing. After providing heuristic motivations for this idea, concrete examples are presented, and the stability of solutions as well as the numerical methods required to find generic solutions are discussed. A general prescription for characterizing no-boundary instantons is developed, before examining explicit minisuperspace models. A special emphasis is put on the appropriate boundary conditions, both in the path integral formalism and in the Wheeler–DeWitt equation. The robustness of solutions upon the inclusion of expected quantum gravity corrections is discussed, as well as the question of which kinds of complex metrics should be allowed. This leads to a discussion of both postdictions and predictions of the proposal.