 Welcome to this course on Introduction to Reciprocal Space. We are all familiar with the real space which is the standard, you know, x, y, z or x, y, z coordinates, the Cartesian coordinates as they called. But both in physics as well as material science, there is a lot of work that is carried out in what is described as reciprocal space. In as the word suggests, it is something of an inverse of the real space. And there are many specific aspects of both physics as well as material science which are much better described and much better presented in reciprocal space. So in this course, I will introduce you to what reciprocal space is and what its utility is. So for example, in material science, it's used to understand things like diffraction patterns. In physics, it's used to understand things like band diagrams. How do band diagrams originate? But however, when you take books on material science, the treatment of reciprocal space follows a certain process, a procedure. And if you take physics books, they follow a certain different procedure. And often, it's not immediately apparent how they relate to each other. In this course, which is about 10 hours long, I hope to show you exactly what reciprocal space is and also to show you enough information that you can, you will easily relate what is shown in a physics book to what is shown in the material science book and then have much more confidence in how you would utilize this information. So for this course, we will use a particular book. This is the book called Physics of Materials. It's also called, I mean, Essential Concepts in Solid-State Physics. This is a book that I have written. And it has specific chapters exclusively on reciprocal space and its use in physics in understanding solids and so on. Both the material science aspects as well as the physics aspects are explained here. So we will use this book. And when we are done, you will understand all the notation associated with reciprocal space and how it is used. I hope you'll benefit from this course. I am confident you will if you are interested in this area of activity. Thank you.