The effect of various natural substances and chemical compounds on their targets is often unknown. In order to carry out a target-oriented drug discovery efficiently, targets and a corresponding test are required. These tests are usually based on a binding or catalytic function, which is usually visualized by optical methods. The drug tests can then be cell- or enzyme-based. In many cases, these tests are complex and expensive. In order to optimise this, a highly miniaturised microarray-based test for proteins has been developed, which can be carried out with very small amounts of material. Purified proteins are then the targets for the active ingredients, exploiting the binding properties of the targets for ligands or the like in order to test possible active ingredients and their chemically optimised derivatives. Targets of different proteomes such as Hsp90, Hsp70 and others as signatures of cellular stress or pathogenesis can thus be investigated with regard to drug susceptibility or diagnostics. Further fields of application of the microarray system are the determination of protein interactions, transport processes in artificial or natural vesicle systems or protein crystallization.