Optical genome mapping (OGM) is a non-sequencing-based genome technology used to detect large-scale structural and copy number variations in a genome. OGM enables detailed characterization and mapping of large-scale genomic anomalies, and it closes a gap between (molecular) cytogenetics and next-generation sequencing approaches. The sole use of OGM is not recommended, as OGM has limited and uneven resolution, epigenetic changes such as uniparental disomy are not accessible, mosaics cannot be clearly resolved, and heterochromatic regions are not accessible.