A study published in *Nature* (482(7383): 53–58. doi:10.1038/nature10802) investigates the mechanisms by which errors in mitosis lead to DNA breaks and chromosome pulverization, potentially contributing to cancer and developmental disorders. The research focuses on micronuclei, which form when chromosomes lag during mitosis. These micronuclei can persist in cells over multiple generations and may lead to DNA damage and chromosome rearrangements. The study shows that micronuclei undergo defective DNA replication, resulting in DNA breaks and chromosome pulverization. This process may explain "chromothripsis," a phenomenon where isolated chromosomes or chromosome arms undergo massive DNA breakage and rearrangement in cancer and developmental disorders. The study also demonstrates that chromosomes within micronuclei can be distributed to daughter nuclei, potentially integrating into the genome. The findings suggest that mitotic errors can lead to mutations and chromosome rearrangements that may contribute to tumorigenesis. The research highlights the role of defective DNA replication and impaired DNA damage response in micronuclei, which may lead to chromosomal instability. The study provides insights into the mechanisms underlying aneuploidy and its role in cancer development.A study published in *Nature* (482(7383): 53–58. doi:10.1038/nature10802) investigates the mechanisms by which errors in mitosis lead to DNA breaks and chromosome pulverization, potentially contributing to cancer and developmental disorders. The research focuses on micronuclei, which form when chromosomes lag during mitosis. These micronuclei can persist in cells over multiple generations and may lead to DNA damage and chromosome rearrangements. The study shows that micronuclei undergo defective DNA replication, resulting in DNA breaks and chromosome pulverization. This process may explain "chromothripsis," a phenomenon where isolated chromosomes or chromosome arms undergo massive DNA breakage and rearrangement in cancer and developmental disorders. The study also demonstrates that chromosomes within micronuclei can be distributed to daughter nuclei, potentially integrating into the genome. The findings suggest that mitotic errors can lead to mutations and chromosome rearrangements that may contribute to tumorigenesis. The research highlights the role of defective DNA replication and impaired DNA damage response in micronuclei, which may lead to chromosomal instability. The study provides insights into the mechanisms underlying aneuploidy and its role in cancer development.