Cerebral microinfarcts (CMIs) are small, presumed ischemic lesions that exist at the crossroads of cerebrovascular disease and dementia. Although by definition tiny, CMIs number in the hundreds or thousands in affected individuals, cause measurable disruption to structural brain connections, and associate with dementia apparently independently of Alzheimer’s disease pathology or larger infarcts. There is substantial recent progress in the understanding of CMIs, driven in large part by new in vivo detection methods. Moreover, experimental models have been established that closely mimic human CMIs. Insights derived from these recent advances suggest that CMIs can be manifestations of both small vessel and large vessel disease, that CMIs are independently associated with cognitive impairment, and that they likely cause damage to brain structure and function that extends beyond their actual lesion boundaries. Criteria for the identification of CMIs with in vivo magnetic resonance imaging are provided to support further studies into the role of CMIs in cerebrovascular disease and dementia.