New technological advances offer an opportunity to clarify details of human pathology and pathophysiology. The advent of T2*-weighted gradient-recalled echo magnetic resonance imaging (MRI) allowed recognition of a relatively new finding: brain microbleeds. These lesions are very small (most often 2–5 mm in diameter), round, hypointense foci that were not evident on other standard MRI sequences. Susceptibilityweighted images are probably even more reliable than T2*weighted gradient-recalled echo images for showing these microbleeds. Hemosiderin within these small foci is mostly responsible for producing the alteration in magnetic resonance that allows recognition of microbleeds.