Emotions remain something of a mystery for most of us even when we accept their centrality to development in general and to infancy in particular. I make 2 arguments in this paper. One: that the most crucial thing about emotions is that they allow mutuality of engagement with other emotional beings--not only evoking responses, but also provoking further emotions in others. Mutual engagements--sometimes called moments of meeting or encounters with other minds--can be transformational. They allow us to be "seen," to be "known" by others, and in achieving that, they allow us to be persons. Some key phenomena of emotional encounters in infancy are discussed to illustrate this point. Evidence of such meetings is abundant in our lives and needs a committed focus for study within developmental psychology. Two: that we need to open out the idea of emotions (as well as probe at a microlevel) and the terms "affect" or "affectivity" might help encompass a greater breadth. Daniel Stern's "vitality affects" and Ben Anderson's "affective atmospheres" both cross disciplinary boundaries in contemplating emotional phenomena. It seems crucial for developmental psychology to incorporate such different aspects--neurological, kinematic, situational and sociopolitical--into discussions of emotional development.