Controlling the placement of molecules on large surfaces with nanometer precision is a common goal of photonic, electronic and biosensing. Top-down fabrication (through lithography, deposition and etching) has been a very successful technology to shape matter from the centimeter down to the 100-nm range. Yet, as the technology is pushed further down, it becomes prohibitively expensive to overcome the limitation of diffraction and reach for the 1-100 nm range. Bottom-up assembly is a perfect technology to bridge this gap. Inspired by the robustness and precision of self-assembled biological structures, bottom-up assembly relies on the programmed self-assembly of atoms and molecules to build large complexes (10-100nm) from simple bricks (0.1-1nm). Top-down and bottom-up assembly hold together the potential to tailor the properties of materials down to the atomic scales, thus enabling tremendous new applications. I propose to combine bottom-up and top-down assembly, coupled to single-molecule microscopy and microfluidics, in order to address technological locks in the quantification of biomolecules. By arranging biomolecules with nanometer precision on square millimeter surfaces, we aim to build digital arrays that count digitally many distinct targets, with high sensitivity, high specificity, minimal operations and high reliability. Because the array will be developed with potential applications in mind, a particular emphasis will be placed on robustness, reproducibility and integration.