Cosmic Microwave Background radiation

What is cosmic microwave background radiation and why is it significant? Who discovered it? Cosmic microwave background radiation is a form of electromagnetic radiation that is found everywhere in the universe. It cannot be seen with naked eyes, but is visible with a radio telescope. Through a radio telescope a faint background glow is seen which is almost exactly the same in all directions. This radiation is not associated with any star, galaxy or other object.Its present temperature is about 3 K. The existence of the microwave background is direct evidence that the universe expanded from a hot, dense state. CMBR was accidently discovered by Arno Penzias and Robert Wilson in New Jersey