There is provided herein an implantable device for monitoring a condition of a biological tissue, the device comprising: a sensor comprising a plurality of electrodes spaced apart from each other, an electric signal source configured to provide an electric signal to one or more pairs of neighboring or non-neighboring electrodes of said plurality of electrodes and an electric signal measurement unit configured to measure impedance values between each of said one or more pairs of electrodes wherein said signals produced by said electric signal measurement unit are indicative of a characteristic of a biological tissue adjacent the pair of electrodes.
