We have built an agent-based simulation population called DEMOS (Demographic and Epidemiological Model of Singapore)--a creation of cohorts of virtual individuals based on local aging trends and disease risk based on local studies. It simulates, at the individual-level, the population of Singapore that accurately reflects the current published data on health and other attributes within Singapore, and known scientific research for the incidence, progression and response to treatment of the major illnesses. Through micro agent-based modelling and simulation, risk prediction and risk modification personalised to an individual enables us to simulate possible future scenarios for any single person in Singapore, taking into account the effect of various interventions they may have attempted. One is able then to predict with some reasonable confidence the effect of nature, nurture, choice and chance.