Ultra-high density oligomer arrays and methods for their preparation

The present invention relates to a process for preparing a oligomer arrays. The method comprises the steps of: providing a substrate having a plurality of recesses; Introducing a first particle having a first molecule in a recess; Releasing the first molecule from the first particles; Binding of the first molecule to a second molecule to form an oligomer, wherein the second molecule is immobilized in the recess; optionally repeating steps wherein at least one of the first particle and / or the first molecule comprises a detectable marker.