The organic field effect transistor (OFET) is a device where a thin film of an organic semiconductor (OS) bridges a channel between source and drain electrodes. This chapter looks into the OFET as a low-dimensional device and how this distinctive feature can be exploited for a rational design of sensing devices. The chapter provides a brief description of OFET working principles. It reviews different approaches to unconventional fabrication and growth of OFETs. The chapter focuses on the charge injection response, when the OFET acts as a charge tunneling device. It talks about low-dimensional charge transport in OFETs and reviews sensing principles and applications of OFETs. Problems of stability and repeatability have to be addressed for the future, as well as for standardization of the OFET response, but this appears as dominant in the near future, especially in view of implantable devices.