Microdeletion syndrome is characterized by very small chromosomal deletions which cannot be detected through karyotype, the usual process of determining characteristic chromosomal features. The detection is accomplished through fluorescence in situ hybridization (FISH), a technique which employs fluorescent probes to find specific DNA features. Some of the microdeletion syndromes include Angelman syndrome, Prader-Willi syndrome, Williams Syndrome, Smith-Magenis Syndrome, and Miller-Dieker Syndrome). The most common is DiGeorge Syndrome (“insert link”) which involves the deletion of very small genes of chromosome 22nd’s long arm. Many of these syndromes are characterized by developmental delay.