The Affymetrix Genechip platform allows the simultaneous analysis of thousands of human single-nucleotide polymorphisms (SNPs) scattered throught the genome and starting from a little amount of genomic DNA. This system provides highly accurate calls with great reproducibility level. The output is both qualitative (a genotype is assigned to each molecular marker) and quantitative (a copy number estimation is provided), consequently this method allows to conduct different kinds of analysis at a high resolution level.