The project is aimed at the creation and manipulation of atomic density patterns by contact-free self-assembly due to optomechanical forces. We are looking at large patches (samples size of some millimetres) of laser cooled matter (around 100 µK), which will be structured on scales of wavelengths to hundreds of micrometres. The spatial structure is not imposed externally but evolves spontaneously from an instability of the homogeneous atomic cloud in interaction with a homogeneous light field.