This editorial introduces a new special series on intervention development in the on-line open access journal Pilot and Feasibility Studies. An intervention development study reports the rationale, decision-making processes, methods and findings which occur between the idea or inception of an intervention until it is ready for formal feasibility, pilot or efficacy testing prior to a full trial or evaluation. This editorial begins to explore some of the challenges associated with this early research stage. It commences a debate about how to produce novel interventions which are fit for purpose and which solve important health and social care problems. By transparently reporting more intervention development studies, scientific rigour will be improved and everyone can learn from the experiences of others.