Ever since 1898, when Pia took the first photographs of the Turin Shroud, many researchers have advanced hypotheses to account for the body image visible on the most important Relic of Christianity. Until now, many interesting hypotheses have been examined, but none of them can completely explain the mysterious image. This article considers the most important of these hypotheses and concludes that radiation was responsible for the formation of the image. Although this hypothesis is still incomplete, of the various sources of radiation phenomena, corona discharge is preferred.