Diabetes mellitus is a massive public health problem that has major socio-economic implications. There are now local and international data that confirm the high prevalence of diabetes in Chinese populations living in affluent societies such as Hong Kong. The heterogeneity of diabetes mellitus, especially among patients with a young onset of the disease, is being increasingly recognised. Genetic factors appear to be a particularly important factor in these young diabetic patients, who face a long duration of disease. Understanding the pathogenesis and genetic basis of diabetes mellitus and its complications are of fundamental importance to improving the diagnosis and treatment of this heterogeneous disease. Despite its complications, diabetes mellitus is a very treatable and preventable disease. The challenge lies in the effective delivery of quality and affordable care to high-risk individuals. To this end, these concerted efforts among academics, clinicians, scientists, health care professionals, administrators, and policy makers are required to defuse this health care time bomb.