In article number 1900264, Annalisa Convertino, Valentina Benfenati, and co‐workers show that a forest of randomly oriented gold coated‐silicon nanowires (Au/SiNWs) induces the differentiation of astrocytes showing complex structural and functional properties in vivo. Tight junctions between the Au/SiNWs‐device and astrocytes processes enables extracellular recording of slow‐frequency oscillations generated only by differentiated cells.