Recently in the UN General Assembly (UNGA), India has declared that nuclear energy is crucial for meeting the challenge of climate change and suggested measures to increase its public acceptance. It has to be noted that, nuclear energy has been receiving stiff opposition and some countries even plan to phase out their nuclear power plants due to their inherent risks. In this article, you will learn what is nuclear energy? How do nuclear reactors work? What are the advantages and disadvantages of nuclear energy? How nuclear fusion different from fission and its advantages and challenges? What is the stand of different countries? What is India's 3 stage nuclear power programme? What are the advantages and disadvantages of thorium-based reactors? and What is the current status of the 3 stage programme and its challenges?