Introduction MRI, Magnetic Resonance Imaging, also known as Nuclear Magnetic Resonance Imaging (NMRI), and Magnetic Resonance Tomography (MRT). The MRI scanner is relatively a new device of medical imaging, non-invasive, that demonstrates the interior of the human body. The roots of the MRI technology are based on a principle first discovered in the late 1930s - magnetic resonance (MR). One of the first applications of this principle was a device called Nuclear Magnetic Resonance (NMR). NMR is used to identify the atomic and molecular structure of chemicals. The MRI scanner, the most popular, commercial and known use of the Magnetic Resonance Principal, is a development of the NMR device that made it possible to get a 3D accurate picture of internal organs in the body. These pictures have significantly improved diagnostic ability and are helping surgeons to understand the anatomy and pathology better before surgery. The Magnetic Resonance Principal is the base of many implementations other than NMR and MRI, some of them based on nuclear magnetic resonance, and some of them based on electronic electron resonance (Electron Paramagnetic Resonance, EPR), such as accurate atomic clocks, Maser (The equivalent of the laser, only in microwaves), methods of characterizing defects in materials and more. The research today is implying that in the future this principle can help develop other implementation in various fields. This book is divided into five chapters that describe the magnetic resonance technology as a whole and MRI in particular. Chapter I – The History of MRI. In this chapter, we will briefly describe the sequence of events from the discovery of the NMR, through the invention of the CT, to the invention of the MRI, and get familiar with the stories of the people who contributed to these discoveries. At the end of the chapter, we will discuss the controversy that broke out when the Nobel Prize was not awarded to one of the founders of the idea- a prominent figure in this fieldRaymond Vahan Damadian. Chapter II – Basic Concepts. In this chapter, we will present the basic concepts in the physics of magnetic resonance, in order to lay the foundations for understanding the following chapters, even for those who have no background in physics. We will examine the term Nuclear Magnetic Resonance Imaging and explain each of the words in a separate section. In the first section we describe the structure of the atom; In the second section we will focus on the phenomenon of electromagnetism and its expressions at the various levels in the MRI scanner; In the third section we explain the phenomenon of resonance in general and the magnetic resonance in particular; In the fourth section we will deal with the imaging itself, the elements of image creation and the process in which the digital data passes through the computerized systems of the hospitals. Chapter III – The Physics behind the MRI. This is the central chapter of the book. Here, we will learn the physical principals of Magnetic Resonance as its being expressed in the MRI Scanner. We will demonstrate gradually, methodically and clearly the physical factors of magnetic resonance. We will describe the Zeeman Effect, the proton precession and the radio pulse at the Larmor frequency. We will also describe the decay processes and explain the terms- T1, T2, PD, TR, TE, and TI. We will see how a signal is generated and present the types of pulse sequences, including fast sequences, such as gradient-echo sequences. We will describe the role of the gradients during the MRI scans, how to connect the signal to the location of the scan area, the role of gadolinium, coil types, Fourier transform, MRI artifacts, how NMR works and many other subjects. Chapter IV – MRI and its position in the world of imaging. In this chapter, we will present the way in which MRI fits into the fabric of today's imaging devices. In the first section of this chapter, we will review in detail and explain all the imaging techniques currently available: X-ray, CT, ultrasound, nuclear medicine, PET scans, SPECT scans and their combinations with CT and MRI (hybrid imaging). Each of the imaging methods is described in detail, regarding its advantages and disadvantages, and indications for its use. The second section will focus on indications for an MRI scanning and the advantages and disadvantages of the use of MRI imaging in relation to other imaging methods. We will also discuss the dangers of MRI and precautions to be taken when using it. In the third section we will describe the types of MRI scanners available today: open MRI vs closed MRI and their differences between them, a small MRI for operating rooms, MRI for breast scanning, special MRI for children, and others. In the fourth section, we will review Special MRI exams that have developed over the years, including MRA (MRI of the blood vessels), MRM (MRI of the breast), MRCP (MRI of bile ducts), DMRI (diffusion MRI), profusion MRI, MRS (MRI spectroscopy), MRE (MRI of the colon), CVMRI (MRI of the heart and blood vessels), MRU (MRI of the urinary tract), MRI prostate, and more. The fifth and final section of this chapter reviews the applications of MRI, for example fMRI (functional MRI), DTI (imaging of the brain's nerve), FUS (use of focused ultrasound with MRI guidance), and more. We will also review the use of magnetic resonance technology in non-medical applications. for example, the use of magnetic resonance imaging for oil pipelines, for nondestructive testing of rocks, wood, and other crops. Chapter V - What Does the Future Hold? In this chapter, we will describe the future of the MRI revolution. We will review the applications and technology improvements, currently under research and development, in the study of magnetic resonance in general, and in the diagnostic MRI and fMRI fields in particular. All of these are based on interviews with scientists and developers from start-up companies that specialize in the recent subject research conducted in the world today. The first section of the chapter describes the future of the study of magnetic resonance and the challenges faced by researchers in this field. The second section describes the attempts to improve the magnetic resonance technology, such as getting rid of the giant magnet by creating a superconductor at room temperature. In the third section, we will focus on improvements in existing MRI scanners, such as General Electric's new Silenz protocol designed to make the MRI test much quieter, and the European INUMAC project, which is trying to develop a scanner with 11.75 Tesla. In the fourth section of this chapter, we will describe the latest news in the development of MRI exams, contrast materials, and MRI software, and in the fifth section we will describe amazing future applications of fMRI, such as lie detectors, robot activation with the mind and communication with people whose condition is defined as vegetative. At the end of the book, you will find an extensive glossary of concepts, presented in the book's chapters, a bibliography which allows you access the relevant literature and expand the knowledge in the fields in which the book deals, and an index. All we have to do is tighten our seatbelts and take off!