Human midbrain organoid microphysiological systems to model prenatal PFOS exposure. (a) Schematics of prenatal PFOS exposure and its effect on brain development. (b) Schematics of human midbrain organoid microphysiological systems (hMO-MPSs) to mode prenatal PFOS exposure. Inserted images of a hMO on the perfusable layer of the holder device (top), and hMO-MPS on a MEA plate (bottom). (c) Immunofluorescence staining showing cell types within one-month-old hMOs: midbrain floor plate progenitor cells (FOXA2), zonula occludens (ZO)-1, early-stage neurons (Tuj1), and neural progenitor cells (SOX2); within two-month-old hMOs: dopaminergic neurons (TH), intermediate progenitor cells (OTX2), astrocytes (GFAP), and mature neurons (MAP2). Scale bar: 50 μm.