Brain microbleeds are small dot-like lesions appearing as hyposignal on gradient echo T2* MR sequences. They represent microscopic areas of old haemosiderin deposits. They are frequent in the setting of symptomatic cerebrovascular disease and also in older healthy people, suggesting a link with cerebral amyloid angiopathy. Their use as diagnostic or prognostic biomarkers remains uncertain. More recently, they have been highlighted as a potential key factor in the pathogenesis of Alzheimer's disease, connecting the main pathological contributors of amyloid accumulation and cerebrovascular damage. The increasing use of MRI in clinical practice and research has brought brain microbleeds very much to our attention, raising many clinical dilemmas, such as—what do they mean? Should I treat a patient with antithrombotic drugs or thrombolysis? And many others.