Children start taking into account and talking about internal states in the second part of the second year when they begin referring more generally to decontextualized, non perceptible and subjective aspects of experience. This is a very important milestone in children's socio-communicative development, showing fundamental emerging abilities in practical "theory of mind" (ToM). It is however only a first step of a long developmental process taking place as the child deals with activities and levels of increasing complexity. This paper presents first evidence by which children provide first signs of implicit comprehension of their interlocutors' internal states through nonverbal behaviors and thourgh informative uses of language. Then, the emergence of talking about and taking into account internal states are analyzed concomitantly in the longitudinal study of one French-acquiring child followed between the ages of 15 and 27 months. The data consist in naturally-occurring interaction videorecorded at the child's home. Results show that emotional and intentional states precedes taking into account the partner's epistemic states (informative uses of language) which, in turn, precedes talking about them. Then, drawing on narrative data from 5 to 10 years old children, it will be shown that internal state talk presents new challenges as children work at higher levels of explicitness and complexity, as the internal states draw on beliefs, and as this talk needs to be integrated to a multidimensional cognitive activity such as the construction of a coherent story out of a sequence of images.