Will we know ET when we see it?

The article focuses on the aspects of the research and identification of extraterrestrial (ET) being on Earth. Topics discussed include the introduction of various basic criteria in determining living from nonliving things, the development on the researches on ET following the discovery of exoplanets beyond the solar system, and the evidences of shadow terrestrials through the desert varnish, a dark stain found on the sunny sides of rocks in arid areas.