The various types of silver halide microcrystals used in the photographic industry are all obtained by precipitation techniques. Highly insoluble silver and halide salts are used and the high kinetics of the nucleation and growth phenomena involved in the precipitation process often limit their capability to be scaled without further costly and time-consuming reformulation. A new concept of "scaleable reactor" for the precipitation of silver halide microcrystals has been developed. which allows to greatly speed-up or even eliminate the translation work between scales. It is based on the simple evidence that, in highly nonlinear systems such as precipitation reactors, scale-up is better ensured when all the critical parts of the process are exactly the same at all scales. Therefore. the concept of scaling by replication instead of the conventional scaling by dimensional changes according to phenomenological laws was studied further. The system presented in this paper uses both batch reactors and auxiliary side-arm loops containing elementary cell(s) in which all the reactants are separately injected. The side-arm loops are connected to the batch reactor which acts as a holding tank and in which only slow kinetics reactions, such as Ostwald ripening, take place, so that the reaction zone remains separated from the bulk. Scaling is ensured by the exact replication of the side-arm loop, the number of replicates being equal to the scale-up factor. while the batch reactor volume varies accordingly to the scale-up factor. The design of the elementary cell, based on the principle of Tee-mixers, was carefully optimized. The batch reactor designs were also studied at several scales, and macromixing compared at different scales, A large range of experimental results are available, demonstrating the validity of the concept for several sizes and morphologies of silver halide crystals.