• Microwell geometry precisely controls the size of hiPSC-derived motor neuron precursor spheroids, enabling reproducible production in the 40–140 μm range.
• Digital Light Processing 3D printing allows rapid fabrication of customizable agarose microwell arrays with distinct aspect ratios, facilitating scalable and standardized spheroid generation.
• Spheroid size and morphology significantly influence the expression of motor neuron differentiation markers MNX1 and ISL1, highlighting the role of geometrical confinement in neurogenesis.
• The developed platform offers a high-throughput, accessible approach for generating size-controlled neuronal spheroids, with potential applications in disease modeling and drug screening.