Machine learning for microwave applications started in the 1990s in the form of artificial neural networks (ANN) for RF/microwave design. Presently, machine learning and artificial intelligence (AI) have become one of the most active topic areas in microwaves, with applications ranging from microwave design automation, to biomedical, security, intelligent wireless systems, and more. This presentation starts with a brief description of historical developments, and highlights some of the state-of-the-art research, and emerging directions in the area.