During the evolution of eukaryotic cells, the majority of mitochondrial genes have been transferred to the nuclear genome with the consequence that most mitochondrial proteins have to be imported into the organelle. This process occurs usually in a post-translational manner. In order to accomplish this task elaborate protein machineries have evolved that import precursor proteins in a concerted fashion and sort them into the four mitochondrial subcompartments. Native techniques such as Blue Native Electrophoresis allow to analyze the composition of the import machineries and to characterize the cooperation of import components. The analysis has led to the discovery of new components and import pathways of mitochondria.