3D printing and bioprinting are recognized as key technologies for the construction of complex micro-devices, microenvironments, and culture models. Thanks to their potential to produce precisely heterogeneous and 3D architectures, multimaterial printing methods, which enable the production of functional 3D structures integrating multiple materials, have attracted specific attention. Nevertheless, combining multimaterial and high-resolution printing is still a major challenge, and the available technologies do not provide simultaneously the resolution and multiplexing capabilities required to create heterogeneous 3D environments. In this work, we introduce the 3D-FlowPrint concept, which involves an opto-microfluidic printhead immersed in a liquid and moved above a surface. This technology combines the convenience of microfluidics in terms of the handling and delivery of small volumes of materials with the resolution provided by laser lithography. Delivered materials are hydrodynamically confined under the printhead owing to controlled aspiration of the injected material, ensuring a continuous supply of material and avoiding cross-contamination issues. Combining microfluidics with photo-polymerization provides unique advantages as it separates the polymerization process from the material delivery, permitting high-resolution polymerization (down to 10 μm) and multimaterial handling (switching time below 60 s). We present a first proof-of-concept using poly(ethylene glycol) diacrylate (PEGDA)-based hydrogels as a photosensitive material model, along with a detailed investigation of the influence of exposure parameters, printhead velocity, and hydrodynamic parameters on the fabrication of 2D and 3D heterogeneous structures. 3D-FlowPrint allows the creation of sub-millimetric to millimetric scale objects with multimaterial designs. A first validation was performed to show the potential of the approach in biology for the creation of engineered microenvironments for cell culture.