Microsatellites, or simple sequence repeats (SSRs), are tandemly repeated DNA sequences of 1–6 base pairs. They are widespread in both prokaryotic and eukaryotic genomes, including the smallest bacterial genomes. Trinucleotide repeats are of particular interest due to their role in human neurodegenerative disorders and some cancers. Microsatellites are found in both protein-coding and noncoding regions and are thought to play a significant role in genome evolution by generating and maintaining genetic variation. Their distribution varies across different genomic regions and taxa, with trinucleotide repeats being most abundant in protein-coding exons across all species. However, in intergenic regions and introns, hexanucleotide repeats are more common. The abundance of microsatellites is influenced by the length of the repeated unit and taxon-specific factors. The distribution of microsatellites in exons, introns, and intergenic regions shows distinct patterns, with some repeats, such as (CCG)n•(CGG)n, being particularly abundant in intergenic regions but absent from introns. The study also found that (A+T)-rich repeats are more common in many taxa. The mechanisms underlying microsatellite distribution, such as DNA polymerase slippage and unequal recombination, are not sufficient to explain all observed variations. Other factors, including DNA mismatch repair and homologous recombination, may contribute to microsatellite instability. The study analyzed microsatellite distribution across various eukaryotic taxa, including primates, rodents, mammals, nonmammalian vertebrates, arthropods, C. elegans, plants, yeast, and fungi. The results show that microsatellite abundance varies significantly between taxa and genomic regions, with rodents having the highest number of microsatellites and C. elegans the lowest. The study also found that certain repeat types, such as (CCG)n•(CGG)n, are characteristic of vertebrates but not other taxa. The findings suggest that microsatellite distribution is influenced by multiple factors, including repeat type, genomic location, and genetic-biochemical background. The study highlights the importance of considering taxon-specific variations in microsatellite distribution and the role of various mechanisms in shaping microsatellite abundance.Microsatellites, or simple sequence repeats (SSRs), are tandemly repeated DNA sequences of 1–6 base pairs. They are widespread in both prokaryotic and eukaryotic genomes, including the smallest bacterial genomes. Trinucleotide repeats are of particular interest due to their role in human neurodegenerative disorders and some cancers. Microsatellites are found in both protein-coding and noncoding regions and are thought to play a significant role in genome evolution by generating and maintaining genetic variation. Their distribution varies across different genomic regions and taxa, with trinucleotide repeats being most abundant in protein-coding exons across all species. However, in intergenic regions and introns, hexanucleotide repeats are more common. The abundance of microsatellites is influenced by the length of the repeated unit and taxon-specific factors. The distribution of microsatellites in exons, introns, and intergenic regions shows distinct patterns, with some repeats, such as (CCG)n•(CGG)n, being particularly abundant in intergenic regions but absent from introns. The study also found that (A+T)-rich repeats are more common in many taxa. The mechanisms underlying microsatellite distribution, such as DNA polymerase slippage and unequal recombination, are not sufficient to explain all observed variations. Other factors, including DNA mismatch repair and homologous recombination, may contribute to microsatellite instability. The study analyzed microsatellite distribution across various eukaryotic taxa, including primates, rodents, mammals, nonmammalian vertebrates, arthropods, C. elegans, plants, yeast, and fungi. The results show that microsatellite abundance varies significantly between taxa and genomic regions, with rodents having the highest number of microsatellites and C. elegans the lowest. The study also found that certain repeat types, such as (CCG)n•(CGG)n, are characteristic of vertebrates but not other taxa. The findings suggest that microsatellite distribution is influenced by multiple factors, including repeat type, genomic location, and genetic-biochemical background. The study highlights the importance of considering taxon-specific variations in microsatellite distribution and the role of various mechanisms in shaping microsatellite abundance.