What subject is HKU famous for?

I'm curious to know, in the realm of academia and research, what particular field or subject area has earned The University of Hong Kong, or HKU for short, a reputation for excellence and prestige? Are they renowned for their groundbreaking discoveries in science, engineering, or perhaps the humanities? Or does their fame stem from a more specialized field, like business or finance? I'm eager to learn about the area that has solidified HKU's status as a leading institution of higher learning.