The methods used in biomedical research are becoming inadequate to meet current challenges. Frequently occurring problem is the need to find the differentiation tests according to phenotypic features or the particular phenomenon. Previously used morphological evaluation or other laboratory tests many times do not allow for adequate determination of differentiating attributes. In recent years there has been considerable scientific and technological progress in the fields such as genomics, transcriptomics, proteomics and metabolomics, which allow to move the search area into the molecular level. It allows the use of advanced molecular techniques such as PCR or oligonucleotide microarrays and thus allows to compare the gene expression profiles of different types of cells and tissues. The microarray experiment data allow to determine the correlation between the expression of selected genes or even entire genotypes of the phenotypic features, characterizing the studied group. The collected data can not be analyzed using traditional statistical methods, since the number of cases is much higher than the number of considered attributes. For this reason, new statistical methods and procedures are used for microarray data analysis which may focus on theoretical or practical aspects. Theoretical aspect is related to the selection of specific genes expression, finding the ontology or metabolic pathways that are associated with the analyzed phenomenon. The practical aspect can be the creation of a predictive model that can allow to predict the specific phenonon occurrence in the future during the studies of new patients. Microarray experiments and analysis of the obtained results begin new chapters of particular phenomena investigation, which is another big boost in the biomedical sciences development.