Another crucial contribution of imputation is that it also facilitates combining genetic and genomic studies that used different genotyping platforms for their experiments. For example. although 415 million common and rare genetic variants exist in the human genome,the current genotyping arrays such as Affymetrix and Illumina microarrays can only assay up to 2.5 million SNPs. Therefore, imputation analysis is an important research direction and it is important to identify methods and platforms to impute high quality genotype data using existing genotypes and reference panels from publicly available resources, such as the International HapMap Project and the 1000 Genomes Project.