This chapter provides a brief overview about micronuclei and their postmitotic fate. Micronuclei are small chromatin-containing bodies formed during mitosis and located in the cytoplasm. Micronuclei have been known for more than 100 years and used as biomarkers for decades, but their fate after formation and with that their biological relevance for the organism has only been addressed in recent years. Four major fates of micronuclei are known: extrusion, reincorporation, degradation, and persistence. Generally, most micronuclei persist without any changes. Around one quarter of the micronuclei are reincorporated into the main nucleus during one of the next mitoses. Degradation and extrusion only occur rarely under special circumstances. Mechanistic backgrounds are still not well understood.