Abstract: The concept of thermal cloak is of exceptional importance, both practically and scholastically. This article provides an overview of the emergence of thermal cloak, while highlighting its unique value in infrared thermal protection for underground shelters. After fifteen years of development and recognition, it is as yet relatively unfamiliar to those outside the field. The special academic value of thermal cloak is also discussed at the end of the article, focusing on its conceptual extension from the lesser concept of “thermal cloak”to the broader concept of “thermal metamaterials”and further expanding to the larger concept of “diffusion metamaterials.” Additionally, this article also discusses the principle and methods of fabricating thermal cloaks.