David Celermajer’s seminal contribution to science has been the invention of a technique to allow the study of the arterial endothelium in humans, and subsequently the first ever demonstration that arterial damage can occur in children and young adults at risk of vascular disease, e.g. in association with passive smoking and obesity, many years before the disease causes complications such as heart attack or stroke. This identification of pre-symptomatic arterial damage has revolutionised the field of cardiovascular prevention and has led to novel treatment options (such as oral L-arginine and inhaled nitric oxide) for patients with early arterial damage.