The book is devoted to the presentation of the physical foundations of microwave sensing of the Earth and its atmosphere. Peculiarities of microwave radiation generation in atmosphere-Earth surface system are considered. The main attention is paid to the tasks that give a practical way out: determining the humidity of the air, the water content of the clouds, the cohesion of the ice, the humidity and temperature of the earth's covers. The book summarizes the experience of satellite measurements in the microwave range. These measurements were made for the first time in the world on the Cosmos-243 and Cosmos-384 satellites in 1968 and 1970. and gave new geophysical results and new methods of remote sensing. Currently, interest in microwave sensing has increased sharply both in our country and abroad - satellites with microwave radiometers began to function in the United States in 1973. Based on the experience gained, promising tasks of satellite and ground-based microwave sensing in combination with other means have been considered. The presentation is largely based on the original results obtained by the authors.