1982 to 1987: He earned his medical degree, finished his dermatology residency as well as clinical fellowship at Xuzhou Medical College and Beijing Medical University before becoming an attending dermatologist in China. He believes that seeing 70+ patients with various skin problems every day has been a real plus in enhancing his clinical sophistication.

1987 to 1994: He completed skin research fellowship at the University of California - San Diego and subsequently conducted research and teaching there as a research faculty. The focus was on the effect of ultraviolet light on skin. He was the first author and co-author of many publications originated from his research in internationally reputable journals. He was awarded three times by the Dermatology Foundation with financial supports in "recognition of the contributions made to expanded knowledge in the field of dermatology."

1995 to 1999: Furthered his clinical training by graduating from an internship at Loyola University, Chicago and a dermatology residency at the University of California - San Diego. Since he had already significant clinical experience in dermatology, he focused his residency this time on dermatological surgery including Mohs micrographic surgery to treat skin cancers. Cosmetic dermatology including laser treatment was another aspect into that he paid lots of attention.

Since 1999: Dr. Yen had been a full-time clinical faculty in the Department of Dermatology at the University of California - Davis, where he taught dermatology and dermatological surgery until six years ago when he decided to split his time between teaching at the university and his private practice. He had served as Chairman of Quality Assurance Committee and Director of Phototherapy Unit in the department. Currently, he is a part time clinical faculty member at UC Davis.