A grid assembly for cryo-electron microscopy may be fabricated using standard nanofabrication processes. The grid assembly may comprise two support members, each support member comprising a silicon substrate coated with an electron-transparent silicon nitride layer. These two support members are positioned together with the silicon nitride layers facing each other with a rigid spacer layer disposed therebetween. The rigid spacer layer defines one or more chambers in which a biological sample may be provided and fast frozen with a high degree of control of the ice thickness.