A high-level overview of different types of biosensors with their advantages and applications is presented. Optical biosensors can be made based on optical diffraction or electro-chemiluminescence. Thermal detection biosensors exploit fundamental properties of biological reactions, namely absorption or production of heat, that in turn changes the temperature of the medium in which the reaction takes place. Electrochemical biosensors are mainly used for the detection of hybridized DNA, DNA-binding drugs, and glucose concentration. Amperometric is a high sensitivity biosensor that can detect electroactive species present in biological test samples. Biosensors that use holograms as the sensing element can have potential applications in screening pancreatic disorders at lower price. The most commercially successful biosensors, amperometric glucose biosensors, have improved the quality of life for people with diabetes.