With scientific developments, certain new technologies based on such scientific principles have now been adopted worldwide. This has resulted in complete or partial eradication of some old technologies. Changes in technologies have become more apparent after the midtwentieth century. The world prosperity has improved now, and constrains of the Second World War are no longer felt. Thus the light production using incandescent lightbulb has now become a thing of the past, while fluorescence-based light production has resulted in saving large amounts of generated electric power. Thermal steam–powered (coal-based) locomotive are now completely replaced by diesel and electricity-powered locomotives. Technological changes are constantly being reported in the news. Even before this book was published, in which the replacement of electronic tubes (valves) by silicon-based transistors was included as a chapter, now there is report of carbon nanotubes replacing transistors. In agriculture, there has been a report of a genetically engineered plant (TomTato) that shall produce both potatoes and tomatoes. Human memory is short-lived. The purpose of the present book is to demonstrate such changes, with selected examples only. I hope more of the younger generation shall learn that the technologies, which they are now using, had their old predecessors. Human memory is short-lived. The new generation may not be aware of a once-useful technology getting extinct or being replaced due to the development of a better and stronger new technology. Examples of such changes are numerous, but here we have only used selected examples to illustrate such changes.