The aim of the dissertation is to contribute with knowledge about mathematizing in preschools\, by empirically and analytically exa mining mathematizing as accomplished in children’s multimodal interactio ns with each other and their pedagogues in everyday activities. Theoreti cally and analytically the dissertation is based on an ethnomethodologic al and conversation analytic perspective (EM/CA) (e.g. Goodwin\, 2000\; Heritage\, 1984)\, which highlights multimodal interaction and communica tion in social contexts. Mathematizing is defined as participation in ma thematical discourse (Sfard\, 2008). A special interest is directed to h ow preschool children use talk\, embodied actions and other semiotic res ources as they orient to mathematics in play and other activities. The d issertation is based on ethnographic fieldwork combined with video recor dings of everyday mathematizing in two Swedish preschools with children 3–5 years old.

The findings are presented in three studies. *Th
e first study* examines how mathematical activities emerge in childr
en’s interactions with each other and with their pedagogues. Whether it
is the children or the pedagogues who initiate the activity\, the childr
en are shown to be actively involved in the construction of the emerging
mathematical content. Geometric shapes as well as different aspects of
number sense are a couple of the mathematical topics covered in the stud
y. *The second study* explores children’s mathematizing in the bl
ock play area\, with an interest in preschoolers’ displayed understandin
gs of geometry (spatiality\, shape\, symmetry) (Seo\, 2003). The study d
emonstrates how the participants orient to different spatial phenomena a
s they work with a construction toy. The children are shown to rely upon
verbal and embodied resources such as deictics and pointing gestures as
geometrical aspects are actualized in their interaction. *The third
study* investigates mathematizing with an interest in how geometrica
l shapes are made relevant in interaction in two consecutive pedagogical
activities: reading and painting. The results of the study demonstrate
how naming (baptizing) (Sfard\, 2008) of geometrical shapes are central
in the two activities. In the painting activity an aesthetic dimension w
as actualized in the children’s discourse\, that somewhat obscured the m
athematical content in the activity. The study thus shows the complexity
of the relations between the activities. Together the studies contribut
e with knowledge on preschool children’s everyday mathematizing\, in par
ticular children’s appropriation of a geometric discourse as it emerges
in the unfolding flow of multimodal interaction. Through the use of an E
M/CA perspective the dissertation contributes with new theoretical and m
ethodological approaches to research on mathematics in preschools.