Researchers found that approximately one in 40 human bone marrow cells carry massive chromosomal alterations without causing any apparent disease or abnormality. Even so-called normal cells carry all sorts of genetic mutations, meaning there are more genetic differences between individual cells in our bodies than between different human beings. The discovery was enabled by a single-cell sequencing technology called Strand-seq, a unique DNA sequencing technique that can reveal subtle details of genomes in single cells that are too difficult to detect with other methods.