A chemical reactor and method for operation. The reactor enables N pairwise fluid contacts among k chemical fluids, with k≥2 and N≥4 and comprises: a reaction layer extending in a plane subtended by two directions; N chemical cells, each including two circuit portions, designed for enabling circulation of two of the k chemical fluids, respectively, the two circuit portions intersecting each other, thereby enabling one pairwise fluid contact for the two of the k chemical fluids; and a fluid distribution circuit comprising: k sets of inlet orifices sequentially alternating along lines parallel to one of the two directions, for respectively dispensing k chemical fluids to the reaction layer; and k sets of outlet orifices sequentially alternating along lines parallel to the inlet orifices, for respectively collecting k chemical fluids from the reaction layer, and wherein, each circuit portion connects an inlet orifice to an outlet orifice.