In the developing brain, precise regulation of WNT signaling pathways is essential for neural progenitor proliferation, patterning, and cell-fate decisions. Our lab is using an optogenetic approach to manipulate WNT3A activity with spatiotemporal resolution in three-dimensional human brain organoids. By fusing WNT3A to a light-sensitive protein domain, we can trigger or halt its secretion simply by illuminating targeted regions—allowing us to dissect how dynamic WNT3A gradients sculpt early neurodevelopmental processes. This platform provides control over a key morphogen, enabling new insights into human brain patterning and paving the way for models of WNT-related neurodevelopmental disorders.