Through daily exposure to the surrounding input structured in conversations, children's language gradually develops into rich linguistic constructions that contain multiple cross-modal elements subtly used together for rich communicative functions. Children demonstrate their skills to resort to multiple semiotic resources in their daily interactions and expertly use them according to their expressive needs and communicative intents. Usage-based (Tomasello, 2003) and cognitive linguistics (Langacker, 1988) as well as construction grammar (Goldberg, 2006) have enriched our comprehension of the processes at work. Those approaches need to be combined to gesture studies (Kendon, 1988;McNeill, 1992) and multimodal approaches (Andren, 2010;Morgenstern, 2014) to fully capture the orchestration of the semiotic resources at play (Cienki, 2012;Müller, 2009). But child language development cannot be understood outside its interactional, dialogic context (Bakhtin, 1981) and without taking into account the role of expert languagers (Vygotsky, 1934) in routines or formats (Bruner, 1975). The first section thus extensively focuses on a productive combination of theoretical approaches and methods, which have been essential to understand child language development, but analyzing child language is also necessary in turn to ground socio-cognitive and interactional approaches to language. The salient features of the variably multimodal child's development are presented in the second section. The third section illustrates longitudinal pathways into multimodal languaging thanks to detailed analyses of adult-child interactive sequences.