My happiness was on the top of the heaven when the first Indian designed nuclear submarine viz. INS ARIHANT was commissioned by Indian navy in 2016 wherein my research has been used. It is a rare occasion in the life of a scientist to see that his research has been applied in his lifetime. I was fortunate to experience this. I was again fortunate that I could get an opportunity to work equally on theory and experiment. The computer code CONTRAN was developed on my own when such codes were not available from the world, post 1975 nuclear tests done by India at Pokhran. I can confidently say that it is the most robust code and can handle all given situations and can be used for the purpose of validation/licensing of nuclear power plants. I took VRS from BARC in 2006. But I am very happy to share with you that the computer code CONTRAN is very much in use at BARC. It is an exceptional phenomenon in the life of a scientist that his research work will be carried forward and put into continuing usage and development, even after his retirement from the department. I came to know recently that it has now been upgraded with capability to simulate a number of nuclear reactor safety systems. This upgradation is being continued at BARC. My salute to the team working on it. I am sure that this book compiling almost all my publications will be of immense use for the scientists in general and specially at the department of atomic energy.