Pre- or postnatally detected, genetically caused inborn syndromes make a huge contribution to the global burden of such diseases. This section welcomes articles exploring the role of microscopically visible and submicroscopic chromosomal aberrations across the whole spectrum of correspondingly caused clinical genetic syndromes. Studies on the formation of derivative chromosomes are more than welcome. Single case reports need to provide a comprehensive review of the literature of comparable cases. Of special interest are studies on small supernumerary marker chromosomes and complex chromosomal rearrangements including karyotype chaos and chromosomal mosaicism.