What does it mean to be in the world with others? To what degree is sociality a dimension of our experience? This Element explores the social aspects of our experience as shared and common, focusing on Heidegger's thought on this theme in the period surrounding the publication of Being and Time. It begins by situating Heidegger's position in contrast to alternative phenomenological conceptions of the relations between self and others. From there, it continues to address a key challenge to Heidegger's approach: the problem of Dasein's individuation. Finally, in response to this challenge, the work reframes Heidegger's conception of sociality through the prism of part-whole relations. As social, Dasein emerges as a dependent part of an unfolding shared whole, yet as part of a complex social context, it retains its relative wholeness.