Why is the square root of 5 approximately equal to 2.2360679774? How to compute the height of a tree without climbing on it? How to assess the surface of your flat? How to compute the sum of all integers from 0 until the year of your birth in 3 operations, and less than 2 seconds? Why and how are the two main words of this book introducing in a very clear and visual way some of the main concepts and relevant techniques used in calculus. Conceived for first year students in computer science, engineering, mathematics, life science, economy, finance, management or law, this new hands-on tutorial, taking advantage of more than 30 years of practice at universities worldwide, adopts a step-by-step approach, supported by hundreds of examples, and solved exercises.