The chapter explains the rapid development of the child science network in the early Soviet era in the midst and aftermath of the post-revolutionary civil war. All-out ‘struggle’ with ‘delinquency’ and ‘defectiveness’ associated with millions of child vagabonds (besprizorniki), was crucial to the initial phase of expansion. The institutionalization of ‘defectology’, which built on the pre-revolutionary ‘curative pedagogy’, saw particular growth at this juncture. A parallel cause of expansion, which became more dominant from around 1923–4, was the imperative to adjust norms of educational development in order to create an education system for a mass child population that was, for the most part, still being brought up in contexts of exceptionally low levels of literacy and schooling. This took place through progressive educational experimentalism, based on both native and imported models, while at the same time prompting the rooting of the legitimacy of pedagogical innovations in a new science of child development. The chapter also places the expansion of the Soviet sciences of the child in the context of the Bolshevik early 1920s’ ‘revolutionization’ of the human sciences, notably psychology. The analysis concludes by scrutinizing two particularly prominent programmes of innovation in the human sciences of this era—‘reflexology’, based on the neuroscientific paradigms of both Vladimir Bekhterev and Ivan Pavlov; and ‘psychoanalysis’, billed as ‘Freudo-Marxism’. Both thrived in the contexts of trauma and transformation that defined the first half of the Soviet 1920s; though both also failed to survive state-enforced accelerated industrial modernization, which, by the end of the 1920s, introduced new priorities—institutional centralization, political alignment, and social discipline.