As the last frontier of our time, structure exploration, ranging from proteins to nano-materials and systems, has been the pivotal point of the mechanistic understandings and ultimate applications; implied also in the core of many scientific problems under investigation today, as well as in the origin of the modern research enterprise, it inevitably calls for the theoretical foundation and instrumental skills of X-ray diffraction. While XRD has been routinely performed around the globe, the users are often overwhelmed by the massive construction of the paradigm, and obscured by many of its "branches and leaves" from observing the whole "tree," let alone the entire "forest," in spite of the numerous works archived. As a result, a concise and commanding grasp of the basic, yet in-depth explanation, seems much needed still, to provide readers with a stormy touch of the mind, as well as a sweeping overview from the top of the "forest." It is therefore the purpose of the current pamphlet, to fill the gap by offering readers a smooth flow, from high school leveled physics, negotiated stepwise to the in-depth, with equations appreciable even by a mere glance, all the way to the true frontier of nano-structure analysis and determination. The adoption of informal/conversational speech, as well as omission of non-critical constants in the derivation, will also reinforce the concepts in the streamlined framework, helping to inspire a broader readership. With five chapters, the book covers: Introduction (climbing up to see beyond the horizon); From waves and lens to images; Encoding: the basis of X-ray diffraction; The many facets of X-ray diffraction; and X-ray diffraction instruments. In addition, sample exercises and research examples of nanostructure determinations are also provided for the demonstration in the end. To achieve the anticipated concise and sweeping view, the usual references and annotations have been ignored in this pamphlet, which are, nevertheless, quickly