The profusion of eukaryotic genomes continues to amaze geneticists: as low as a few percents of eukaryotic genome length correspond to protein-coding sequences. Eukaryotic genes are commonly separated by long regions, and their coding sequences (exons) are intervened by non-coding ones (introns), which run to tens of kilobases. Extensive chromosomal regions free from genes, intergenic regions and introns contain great numbers of repetitive DNA sequences, most of which are mobile genetic elements or transposable elements (TEs). TEs are divided into two major classes: DNA transposons and retrotransposons. DNA transposons encode a transposase enzyme catalyzing the transposon DNA excision and its integration into a new genomic location (‘cut and paste’ mechanism). Similar to all other TEs, DNA transposons are transmitted vertically from parent to offspring; however, their horizontal transmission between species (sometimes phylogenetically distant) is not uncommon. Unlike other TEs, DNA transposons are found in both eukaryotes and prokaryotes (for review see Feschotte and Pritham, 2007)