Belonging is emerging as an important concept for early childhood education and care. However, it is one that requires further theorisation beyond everyday or romanticised understandings. The politics of belonging provides a potentially productive focus for thinking about belonging in early childhood education and care because of its attention to how belonging in all its complexity works. A key aspect of the politics of belonging is processes of categorisation, or how social categories influence who does and does not belong, who decides and on what basis. In this article, the author complicates the notion of categorisation by bringing it into an encounter with the concepts of lines and segmentarity from Deleuze. The author then uses these concepts to look at video data of an infant aged eight to nine months in family day care, in an effort to illustrate how processes of categorisation, lines and segmentarity were at work. The data suggests that the category of ‘baby’ played a complex and dynamic role in the infant’s experiences at family day care. Nevertheless, the encounter between the data and Deleuze’s concepts suggests that categories cannot ever tell the whole story, and that looking for situations in which categories no longer appear to work, in which they leak and rupture, might lead to new understandings about how belonging works in different early childhood education and care contexts.