The clinical heterogeneity of asthma patients has been increasingly recognised within the last years. Recent studies and articles highlighted the idea of asthma not beeing a single disease but rather a unifying term for multiple phenotypes. Phenotype in this sense is defined as the combination of observable properties of an organism, that are produced by the interactions of a genotype and the environment. In contrast, endotype describes a specific underlying pathophysiological pathway. Linking asthma phenotypes and endotypes in a system biological approach is an important research goal in order to develop targeted therapy, especially for severe asthma.