By their geometric dimensions, biosensors can be arranged into a sequence of macro-, micro- and nanodevices. From this perspective, the present chapter considers mainly electrochemical biosensors and biofuel cells; attention is also paid to other, e.g. chemical, types of sensors that can be prototypes of developed biosensor devices. One of the moving forces of miniaturization is finding conditions when the least amount of material is used. Miniature devices can play the role of biosensors and represent electrodes for biofuel systems. Due to the broad use of the enzyme glucose oxidase (GOD), which acts as a model protein or the base of existing devices, we discuss in detail the planar technology of forming a multichannel nanobiochip based on the immobilized GOD. The prospects of micro/nanostructures are primarily determined by their miniature size, the feasibility of easy duplication and—in production …