In our natural environment there are several known and unknown phenomena concerning their origin. These are all caused by several mechanical, chemical, thermal, electric and nuclear, etc., factors and their interactions. Of all these disciplines the world of electro-magnetic waves has special significance (Fig.1). As a special type of these waves, the infra-red (IR) radiation are characteristic to the thermal impacts, and in special cases it is suitable for measuring the temperature of objects. Thus the world of IR waves help us determine the temperature fields of objects. That is why IR-imaging and its applications are really interdisciplinary science. The discovery of the world of IR waves in our environment needs a sophisticated method, of course. The current paper reviews the determination of IR temperature fields and presents some examples of engineering applications [3,6].