Three-dimensional imaging has become an essential tool in modern health care, enabling accurate diagnosis and treatment planning for a wide range of conditions. In particular, computed tomography (CT) and MRI stand out in providing detailed cross-sectional images of the human body. While both modalities serve critical roles in clinical practice, they rely on fundamentally different physical principles. This review explores the fundamental physics and image acquisition techniques of CT and MRI, including basic principles, technological advancements, advantages, and limitations.