Nucleation rate measurements have become important since they impact the design and control of crystallization processes. These measurements can be performed at different scales and one of the main methods used at the lab scale is Crystal16 (Aventium Technologies). This apparatus can give access to nucleation rates but presents two main drawbacks: (i) It requires a rather large quantity of matter (compound and solvent) and (ii) it cannot differentiate solid phases if the compound presents several forms (i.e. polymorphism). To counter these drawbacks, two strategies can be proposed : concerning (i), a microfluidic system can be used: it allows a drastic reduction of the quantity of matter needed for nucleation rate measurements and the statistical representativity is larger compared to Crystal16. Concerning (ii), Second Harmonic Generation (SHG) measurements can be envisaged: SHG allows the differentiation of phases, providing at least one of the forms crystallizes in a centrosymmetric structure (no SHG signal) and another in a non-centrosymmetric structure (positive SHG signal). The coupling of microfluidics and SHG can thus be investigated with the aim of measuring nucleation rates of at least two forms of a compound presenting concomitant polymorphism. Actually, SHG imaging could lead to the differentiation of the two forms in the same environment. To this purpose, the ortho-aminobenzoic acid (O-ABA) was studied because this compound exhibits concomitant polymorphism. It presents three solid forms: form I, orthorhombic (P21cn), form II, orthorhombic (Pbca) and form III, monoclinic (P21/c). Since only form I has a non-centrosymmetric structure, SHG measurements should give the opportunity to distinguish this form from the two others during any concomitant crystallization. In this communication, a state of the art about this compound will be presented. Starting from crystallization conditions giving rise to concomitant polymorphism at a 10mL scale, we will highlight how this crystallization behavior was reproduced to the submillimeter scale of microfluidics. This is in view to allow the determination of respective nucleation rates of the different O-ABA polymorphs during their concomitant crystallization by using SHG as a differentiation tool.