One key theme to emerge from the domestication of technology literature concerns the social constraints that restrict and shape people’s use of information communication technologies (ICTs) and this is currently best exemplified in constraints on children’s use of smartphones. This is an important counterpoint to the image of children as being empowered by such technologies and more generally their characterisation as ‘digital natives’ pushing boundaries with new technologies. More banally, the smartphone is the most expensive item children and young people routinely carry on them (while certain uses threaten to create considerable running costs). No wonder that such financial considerations alone have a bearing on their choice of device, the apps children download, the services they use, how much they use smartphones and what measures young people take to protect these precious devices. Domestication is specifically known for highlighting time and space constraints, and here we see how adult concerns (of parents and teachers) lead to rules against smartphone use in different public spaces, how fears of the disruptive and the perceived anti-social nature of the technology curtail their use in schools and how parental aspirations to control ‘screen time’, alongside other norms about appropriate times for use, limiting when and for how long children use smartphones at home. Using qualitative interviews with children, parents and teachers from the Net Children Go Mobile project, this chapter shows how a domestication analysis of the mundane realities of children’s environment can provide a basis for caution when faced with the vision of a new generation embracing technologies.