Biosensor is a device which allows measuring of a biological response such as an enzymatic reaction, antibody and DNA binding, as well as an activity of an organelle and the whole cell. The range of physical and chemical phenomena is utilised as a transduction mechanism including optical, electrical, electrochemical, piezoelectric and calorimetric. Despite high performance of label-based approaches, there is a trend towards label-free biosensing due to its simplicity and ability to directly measure the signal without modifying a sample. Recent advances in nanofabrication techniques allowed miniaturization of biosensor design. The versatile applications of biosensors include medical diagnostics, food quality and environmental monitoring. Refereed/Peer-reviewed