The faint radio signal that fills our universe is the echo of the beginning of the universe. This signal, called the Cosmic Microwave Background radiation, was first detected by accident in 1964 but has since been measured in detail by a number of experiments. These measurements provide a rich information set that enables us to determine how the universe began, how galaxies formed and what the eventual fate of the universe might be. I will describe how these observations are made, what we have learnt from them and what we expect to learn from future experiments.