Hydraulics corresponds to a wide variety of fields unified in a marvelous engineering set of models, all of then resting on several basic physical principles and with vast applications. The direct applications go from simple home hydraulic systems, as in our kitchens or bathrooms to the large industrial structures, buildings, factories, all that make modern life possible. The industrial applications are by far the most studied. It is indeed needed to understand the flows on different geometries, and how this flow produces changes in the system, pressure and viscosity, that determines how the fluid is going to behave even in the simplest structure. The complications to compute and make predictions are enormous, it is only with the aid of numerical calculations that some results can be obtained, nevertheless, the control by using valves and several types of pipelines and some other devices that allow us to reproduce the results that we need for control and applications, even when the fluids are in turbulent and complex regimes. The research in this field pursues to understand mostly industrial applications, but some branches are also related to basic science, where the physics is similar, although the equations that rules are different, such as nanofluids, nanosensors devices and nanoparticles motion in a fluid. The aim of this book is to take some practical examples and show the most relevant concepts and methods. We hope it will give a little inside into the physics and techniques involved in the hydraulics engineering.