The Cosmic Microwave Background (CMB) is the afterglow radiation from the Big Bang, filling the universe with a faint glow. It provides crucial evidence for the Big Bang theory and helps scientists understand the early universe's conditions. Discovered in 1965 by Arno Penzias and Robert Wilson, the CMB is nearly uniform in all directions, with slight fluctuations that indicate the seeds of galaxies. Studying the CMB allows researchers to learn about the universe's age, composition, and expansion, making it a cornerstone of modern cosmology.