Emergencies involving forced displacement and refugee populations are often chaotic and volatile. Humanitarian actors struggle to deliver life-saving assistance to affected children and families, which can number in the hundreds of thousands urgently in need of food, water, shelter, protection, healthcare and other services. Refugee emergencies also trigger a chain of political, environmental, socio-cultural and financial impacts and constraints that require a comprehensive response to address the changing needs of refugee children and their families. The humanitarian response must consider what actions can be taken today to prevent immediate risks and also prepare for tomorrow’s threats. These are some of the vital questions and challenges humanitarians face on a daily basis. Another question that is critical to the achievement of long-term goals in a fast-changing emergency context is the question of what has been accomplished and what remains to be done. Which actions and initiatives are most effective in making a positive difference in the lives of refugee children and their families, and what is the evidence to support those actions? What about challenges in the field? What are the most critical obstacles that hinder the humanitarian response and how do the interventions address them? Are there innovations, good practices and integrated approaches that have emerged during the response? How can the promising results be communicated to humanitarian actors, stakeholders and communities in other countries and contexts, to contribute to humanitarian interventions across the world? The case studies presented in this collection attempt to provide answers to these questions by focusing on some of UNICEF’s key interventions in refugee and host communities in Cox’s Bazar since the onset of the Rohingya refugee crisis in 2017