Behind every great adventure is a good story, and writing a book is no exception. Many people contributed to making this book a reality. I would like to thank the many students I have taught at AUEB, whose dedication and support has been nothing short of overwhelming. They should be rest assured that I have learned just as much from them as they have learned from me, if not more. I also want to thank Damianos Chatziantoniou for conceiving a pioneering graduate data science program in Greece. Workable has been a crucible for working alongside incredibly talented and passionate engineers on exciting data science projects that help businesses around the globe. For this, I would like to thank my colleagues and in particular, the founders, Nick and Spyros, who created a diamond in the rough. I would like to thank Subho, Govindan, Edwin, and all the folks at Packt for their professionalism and patience. To the many friends who offered encouragement and motivation I would like to express my eternal gratitude. My family and extended family have been an incredible source of support on this project. In particular, I would like to thank my father, Libanio, for inspiring me to pursue a career in the sciences and my mother, Marianthi, for always believing in me far more than anyone else ever could. My wife, Despoina, patiently and fiercely stood by my side even as this book kept me away from her during her first pregnancy. Last but not least, my baby daughter slept quietly and kept a cherubic vigil over her father during the book's final stages of preparation. She helped in ways words cannot describe.