Tissues are structured assemblies of similar or diverse cells that cooperate to perform specific physiological functions (see Fig. 2.1). These cellular aggregates are embedded within an extracellular matrix (ECM) that provides structural and biochemical support, enabling tissues to maintain homeostasis, facilitate repair, and adapt to environmental demands. In the human body, tissues represent the intermediate level of biological organization, between cells and organs, and are essential to systemic function and integrity. They are not merely passive structures but are dynamic, capable of self-renewal, regeneration, and remodeling under both normal and pathological conditions [1–3].