The study analyses robust, causal evidence of transformational change and its drivers. We approach this topic by systematically reviewing literature that has the potential to document causal evidence for transformational change across a broad set of interventions and outcomes. Our focus is on evidence found in developing countries. We approach this learning exercise directly by looking at the energy sector and indirectly by reviewing the evidence on behavioural change in the public health sector. Both sectors show examples of transformational change with scale, depth and duration. We identify lessons on transformational change from these two sectors that is relevant to policymakers.