Here we describe a facile yet effective route for the fabrication of crystal-like polymer microdiscs with a huge bump at the surrounding edge through hydrodynamic instabilities of emulsion droplets containing hydrophobic polymer and cosurfactant n-octadecanol (OD). This strategy allows for the generation of polymer particles with tunable size and shape by tuning the cosurfactant concentration, emulsion droplet size, and/or solvent evaporation rate. The generation of polystyrene (PS) microdiscs is balanced by the interfacial instabilities of emulsion droplets, crystallization of OD, and capillary flow. Our approach can be extended to different hydrophobic polymers and allows for the functionalization of the discs with tunable chemical/physical properties by incorporating functional species. By introducing magnetic nanopartides, we have been able to manipulate the spatial orientation of the magnetic microdiscs via an external magnetic field. We anticipate this simple and versatile route to be useful for the design and fabrication of well-defined microparticles for potential applications in the fields of targeting, separation, sensing, drug delivery, and formation of advanced materials.