During the early years of our career as data scientists, we were bewildered by all kinds of data science hype. There is a lack of definition of many basic terminologies such as “big data,” “artificial intelligence,” and “data science.” How big is big data? What is data science? What is the difference between the sexy title “Data Scientist” and the traditional “Data Analyst?” The term data science stirs so many associations such as machine learning (ML), deep learning (DL), data mining, pattern recognition. All those struck us as confusing and vague as real-world data scientists! However, we always feel something tangible in data science applications, and it has been developing very fast. After applying data science for many years, we now have a much better idea about data science in general. This book is our endeavor to make data science a more concrete and legitimate field. In addition to “hard” technical aspects, the book also covers soft skills and career development in data science.