Brighi et al. (2021) found that FMRP-KO organoids not only were bigger in size compared to control organoids, but also had an increased number of glial cells, presumably astrocytes, suggesting an important role of FMRP in regulating gliogenesis and the balance of neural and glial development, as shown with 2D FXS iPSC-derived cellular models (Figure 2) [24,56]. The gene discussed is FMR1; the disease is fragile X syndrome.