The in vitro micronucleus test is used for detection of substances ad samples, which can cause structural and numerical chromosomal aberrations (clastogenic and aneugenic substances). Increased micronucleus formation can reflect the formation of chromosomal breaks or incorrect separation of chromosomes during the cell division. In vitro micronucleus test can be used as a replacement method for the standardised in vitro chromosomal aberration assay, especially as a screening method as it is cheaper and faster to perform. In vitro micronucleus assay can be performed on different cell lines (e.g. human hepatoma cell line HepG2, Chinese hamster ovarian cells CHO, human lymphocytes etc.).