Planar MEAs sit under the tissue. Organoids and slices are 3D, so most of the activity never reaches an electrode. Bio-protocol paper from 𝗣𝗮𝗹𝗶, 𝗣𝗮𝗹𝗹𝗮𝘃𝗶, 𝗖𝗼𝗻𝗳𝗼𝗿𝘁𝗶, 𝗲𝘁 𝗮𝗹., 𝘄𝗶𝘁𝗵 𝗟. 𝗠𝗮𝗽𝗲𝗹𝗹𝗶 𝗮𝗻𝗱 𝗘. 𝗗'𝗔𝗻𝗴𝗲𝗹𝗼 on recording 3D models with penetrating HD-MEAs. Read here: bio-protocol.org/en/bpdetail?id=5708