How are microwaves from space detected and what do they tell us about the beginning of the universe?

Microwaves from space can be detected from the use of radio telescopes. Microwaves have been used to test the big bang theory, and this Cosmic Microwave Background (CMB) radiation is a form of microwave that "fills" the universe, that is almost exactly the same in all directions and is not associated with any star or object. The CMB radiation is recognized to be radiation left over from the big bang, or during the early stages of development of the universe.