Bangladesh can duly boast of the status of “Development Puzzle”. The country sustained economic growth averaging 6.7 percent per annum over the last decade; also displayed remarkable advancement in social indicators such as reduction in incidence of poverty, infant and maternal mortality, fertility, food insecurity etc. In driving such socio-economic development in Bangladesh over the last forty years or so, BRAC has played a pivotal role in supporting government initiatives as well as pursuing programmes of its own domain. BRAC is now about 45 years old and this watershed moment provided an opportunity to reflect on the last four decades or so. More importantly, the aim is to look ahead for the challenges that would be confronted by BRAC. In the backdrop of these factors, this book inscribes the evolution of development interventions made by BRAC, including the mistakes made and the lessons learnt, in its efforts to contribute to socio-economic advancement of the country. As usual, that should be alongside the government, the corporate sector, other civil society organisations, and development partners.