Thanks to the Nobel Foundation for permission to publish this Lecture. Here we report the transcript of the lecture delivered by Professor Craig C Mello at the Nobel Prize ceremony. Professor Mello vividly describes the years of research that led to the discovery of RNA interference and the molecular mechanisms that regulate this fundamental cellular process. The turning point of discoveries and the role played by all his colleagues and collaborators are described, making this a wonderful report of the adventure of research. The lecture explains in simple language the importance of this discovery that has added a great level of complexity to the way cells regulate protein levels; moreover, it points out the beauty and importance of Caenorhabditis elegans as a model organism and how the use of this model has greatly contributed to the advance of science. Finally, Professor Mello leaves us with a number of questions that his research has raised and that will require years of future research to be answered.