When the use of embryos in vitro for research was regulated under the Human Fertilisation and Embryology Act 1990 (as amended), regulators tried to navigate the various thresholds that occur in embryonic and research processes through providing clear-cut boundaries – the most well-known of these being the 14-day rule. This chapter offers an examination of this rule as a contemporary example of an existing mechanism in health research that is being pushed to its scientific limits.  This steadfast legal boundary, faced by a relatively novel challenge, requires reflection on appropriate regulatory responses to embryo research, including the revisitation of ethical concerns, and an examination of the acceptability of carrying out research on embryos for longer than 14 days ? I argue that recognising the inherent link between processes and the regulation of the margins of human life, enables us to ask us to ask more nuanced questions about what we want for future frameworks, for example, ‘when is human?’, one that legal discussion often shies away from. Instead I will argue that viewing regulation of embryo research as instance of both processual regulation and regulating for process has the potential to disrupt existing regulatory paradigms in embryo research, and enable us to think about how we can, or perhaps whether we should, implement lasting frameworks in this field.