miRNAs were found to be key regulators in proliferation, differentiation, apoptosis, hematopoesis and oncogenesis. Different cell types have unique and dynamic miRNA expression profiles that could be used to discriminate between those cell types and even between cellular stages. The iGEM Team Heidelberg 2010 will create miRNA binding site patterns enabling the control of any target gene of choice according to the cellular miRNA expression profile. Therefore, we will apply evolutionary methods for creating large miRNA binding site pattern libraries and we will develop two new and powerful methods for miRNA binding site pattern library screening. In parallel, computational modeling will be used for getting information on natural binding site pattern structure in order to enable rational design of complex binding site patterns recognizing certain cellular miRNA expression profiles in the future.