What Have We Already Learned from the Cosmic Microwave Background?

The Cosmic Background Explorer ( COBE ) satellite, and the Differential Microwave Radiometer (DMR) experiment in particular, was extraordinarily successful. However, the DMR results were announced about 7 years ago, during which time a great deal more has been learned about anisotropies in the cosmic microwave background (CMB). We assess the current state of knowledge and discuss where we might be going. The CMB experiments currently being designed and built, including long‐duration balloons, interferometers, and two space missions, promise to address several fundamental cosmological issues. We present our evaluation of what we already know, what we are beginning to learn now, and what the future may bring.