<p>This reprint based on the Special Issue provides a general overview of different biosensors briefly explaining the general approaches to&nbsp;identifying them their construction and their performance. A discussion concerning how the required components of biosensors are combined to perform analytical work is presented. Different signal-transducing mechanisms are discussed particularly those addressing the immobilization of biomolecular components in the vicinity of a transducer interface and their functional integration with electronic or optical devices.</p>