After long negligence of the studies done by Bonghan Kim and Satoru Fujiwara, an intensive investigation into the intravascular threadlike structures called Bonghan ducts was begun in the Biomedical Physics Laboratory of Seoul National University. It led to a method to identify the threadlike structures as Bonghan ducts using acridine orange fluorescence staining. The size, shape, and distribution of nuclei clearly exhibited the features of Bonghan ducts. The Bonghan ducts and corpuscles on the organ-surfaces of rabbits and rats were observed by three independent teams, and their morphological characteristics were studied. Histological aspects obtained by H&E and Feulgen reactions were in agreement with Kim's and Fujiwara's results. Bonghan ducts inside large lymphatic vessels were observed by using the Janus Green B staining method, which completely resolved the long standing question on the possible confusion between Bonghan ducts and lymphatic vessels. The granules (known as San Al), obtained from the organ-surface Bonghan corpuscles, were shown to contain DNA. The nature of San Al motion was also analyzed to reveal non-thermal features and was shown to be affected by UV-A light.