During the past thirty odd years, when the nuclear self-consistent mean-field methods based on effective interactions were developed and implemented, the tensor interactions have been largely ignored. On the other hand, recent experimental studies and shell-model analyses indicate that these interactions may play an important role in several regions of nuclear chart. A unified picture of the role played by tensor interactions throughout the mass table is still missing, and is very much needed. In the present paper, I have reviewed basic properties of the tensor mean fields, and I have illustrated their role in changing the shell structure and masses of nuclei.