We have learned many aspects of tropical cyclones from satellites, especially TRMM and microwave radiometer/scatterometer. These sensors gave us 3-D rain information, 2-D distributions of total column water vapor , SST, sea surface wind and so on in high temporal resolution. Thus we can assimilate the data to the numerical model to improve the forecast and to mitigate the disaster. In this paper we present the current status of the knowledge about tropical cyclone in the view of these sensors.