This paper explores literature on the topic of Augmentative and Alternative Communication (AAC) across settings and partners used by children who have Complex Communication Needs (CCN). Children learning speech are often able to develop expressive and receptive language skills due to exposure to many speech models and rich language interactions. Both the quality and quantity of these interactions help typical children develop language skills rapidly (Sennott, Light, and McNaughton, 2016). However, for children who use AAC, modeling is much harder to access. Sennott et al. (2016) found that AAC users see or hear about 24,000 words modeled for them (a high estimate) compared to 125,000 words per week for speaking children. Because AAC communicators often lag behind their peers in terms of acquired expressive and receptive language, it is imperative that conversation partners create as much space as possible for these learners to express themselves, whether during interventions or spontaneous conversations, inside or outside of the classroom. For AAC users, an asymmetry often exists between the modalities of input to output. In other words, it is common that an AAC speaker’s ways of expressing language and ways of receiving language often do not match. Studies included in this paper demonstrate that, with the appropriate models of AAC within naturalistic contexts, used with various interaction techniques, the users made gains in both expressive and receptive language. When provided with the right instruction and adequate models, children with CCN can develop flexible language skills (Sennott et al., 2016).