The Cosmic Microwave Background (CMB) radiation is uniform electromagnetic radiation detected throughout the sky, representing the residual heat left over from the early universe. It provides a snapshot of the universe when it transitioned from an opaque plasma state to a transparent, ionized gas. The nearly perfect blackbody spectrum observed today indicates that the early universe was in thermal equilibrium. Minute temperature variations or anisotropies within the CMB are highly significant, as they map the primordial density fluctuations that served as the gravitational seeds for the subsequent large-scale structure, including the formation of galaxies and clusters.