**1. Introduction**

Genetic instability results from alterations induced by agents that severely damage DNA. The nature of the damage may be silent when it occurs in non-coding regions and therefore does not affect the cellular processes of organisms. Still, when damage

occurs in key DNA segments, the biological functionality of cells, tissues, organs, and eventually organisms in a population is compromised [1]. In this sense, genotoxic and cytotoxic damage are indicators of genomic instability. Genotoxicity involves changes in DNA structure such as aneugenic (loss of whole chromosomes) and clastogenic effects (loss of chromosome fragments); whereas cytotoxicity involves alterations in proliferation and cell cycle rate, as well as the magnitude and type of cell death (necrosis and apoptosis) [2, 3].

Various toxicological techniques can assess genotoxicity and cytotoxicity induced by physical, chemical, or biological agents. There are numerous models that can evaluate genotoxicity and cytotoxicity, ranging from biochemical and spectrophotometric tests. These assays depend on sophisticated equipment and the use of expensive reagents and consumables, compared to the set of techniques presented here, which do not require expensive equipment and are accessible to any laboratory with an optical microscope and cell staining systems. Above all, these techniques provide a deep understanding of the biological and cellular mechanisms involved in each model [4].

Assays that record the number of micronuclei (MNi) and other nuclear abnormalities are very versatile, inexpensive, and can be used in a wide variety of *in vitro* and *in vivo* models. Various techniques are based on MNi formation with applicability in the veterinary field, starting from the theoretical principle described in mouse bone marrow [5, 6]. Different techniques were also developed, such as MNi formation in mouse peripheral blood erythrocytes [7, 8] and other mammals (primates, ungulates, felines, and a wide variety of vertebrates, fish, birds, and amphibians) [9–11]. Also, MNi in lymphocytes by cytokinesis blockade (CBMN) is widely applicable in veterinary medicine because it can be developed both in cell lines and in almost any organism (humans, rodents, rabbits, fish, dogs, primates, etc.), whose entire blood volume allows extraction of at least 0.5 mL of whole venous blood [4, 12].

Despite these advantages, techniques based on MNi formation require manual counting with light or fluorescence microscopy. Therefore, reviewer training is crucial due to the time expenditure (2 to 4 hours per slide) and accuracy in distinguishing MNi and other cellular abnormalities [13, 14]. Besides, flow cytometry offers an alternative to reduce the time spent on the microscope by standardizing observations. Initially, this technique required lysing the cytoplasm to release MNi, and thus facilitate their identification [15, 16]. However, this prevents the observation of nuclear buds (NBUDs) nucleoplasmic bridges (NPBs), which are observed in binucleated cells [17]. Subsequently, flow cytometry was improved with image flow cytometry (IFC) techniques that efficiently and automatically record mono-, bi-, and polynucleated cells with and without MNi, NBUDs, and NPBs, which is possible by combining the image flow cytometry technique with the machine learning approach [18].
