A new optical system is presented for a flat-plate micro-concentrator. A single unit is made of an off-axis portion of a paraboloid mirror that focuses sunlight on a photovoltaic cell hidden behind the adjacent unit. This unit can be repeated in a closed-packed two-dimensional array to form a module as large as a conventional flat-plate module, only slightly thicker. Theoretical study shows that an entire module could be molded as a single piece. Tiny solar cells, a few millimeters a side, packaged inside a Secondary Optical Element would be inserted in the module and interconnected from the backside. Each cell would operate at a concentration ratio of several hundreds suns but only require passive cooling because of the small power involved.