Aging can be defined as the result of accumulated cellular damage and deregulation of the epigenome. These changes cause impaired cell maintenance systems, reduced tissue regeneration, weakening of the immune system and increased risk of malignancy. The higher mortality rate in older individuals is a result of these pathologies. The study of age-related changes in adult stem cells and their regenerative potential is crucial to our understanding of the physical deterioration of organs and tissues. The growing interest and knowledge in the field of microRNAs adds a further dimension to this field of research. MicroRNAs are important posttranscriptional regulators of gene expression. They co-regulate stem cell properties such as potency, differentiation, self-renewal and senescence. Various cell systems, e.g. defense mechanisms against reactive oxygen radicals (ROS), DNA repair and apoptosis are regulated by microRNAs. These properties and the assumption that microRNAs act as some kind of general switch make them highly relevant in aging research.