Perovskite solar cells usually adopt the normal or inverted structure, where the active layer is barely isolated from metal contacts and the atmosphere. By coating two conductive glass electrodes with charge transport layers and flowing a growth precursor solution in between, we grew a crystalline 2.7-mu m MAPbI(3) thin plate, thinner than the charge-carrier diffusion length (L-e = 8.7 mu m). After sealing with silicone, the sandwiched structured device withstood boiling water.