Coccoliths of coccolithophorid algae are anisotropically-shaped microparticles consisting of calcite (CaCO3) crystals with unusual morphologies arranged in complex 3D structures. Their unique micro- and nanoscale features make coccoliths attractive for various applications in nanotechnology. It is anticipated that the range of applications of coccoliths can be further extended by (bio)chemical modification and functionalization as well as possibilities for their arrangement into 2D and 3D arrays. However, methods for both aspects are still lacking. The aim of this project is thus to develop methods for regioselective functionalization of coccoliths and their assembly into arrays. Regioselective functionalization of the margin area and central area of coccoliths will be achieved by exploitation of local differences in the composition of the insoluble organic matrix of coccoliths. The existence of local differences in the composition of biomacromolecules within this matrix has only very recently been demonstrated. In particular, we will regioselectively introduce proteins/(poly-)peptides that can serve as “anchoring points” for in vitro modifications into the insoluble organic matrix of coccoliths by genetic engineering of a coccolithophore. These engineered coccoliths form the basis for the construction of coccolith arrays. Three independent approaches for the assembly of such arrays will be pursued. The structural and physico-chemical properties of the coccolith-based magnetite-calcite hybrid material will be determined by means of a number of analytical methods. This interdisciplinary project will benefit greatly from the complementary expertise of the binational groups. In the long term, we aim to create an advanced pool of methods to regioselectively endow coccoliths with desired properties and to develop new biomineral-based materials for nanotechnological applications.