This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book examines the discussion of topics presented before and adds new topics. It deals with the interactive methods section with exploring the history of eye-tracking, followed by a glimpse into the future and describes the application of mobile eye-trackers in psychology, marketing or informatics. The book discusses methodological details in eye-tracking studies, including design decisions, potential pitfalls when running an eye-tracking study, and their solutions and standards for reporting to improve reproducibility. It provides practical guidelines for setting up and running mouse-tracking studies with free software tools, and explores the common assumption of continuity in movement trajectories in mouse-tracking. The book also describes the advantages of combining methods, such as by bringing together verbal protocols, eye-tracking and mouselab. It shows how to use process data to inform cognitive models of decision making.