text: Before the development of the silicon microcantilever, gold foil or tungsten wires were used as AFM sensors. A range of designs of quartz crystal resonators have been used, the most famous is the above-mentioned qPlus sensor. A new development which is getting attention is the KolibriSensor, using a length extensional quartz resonator, with a very high resonant frequency (~1 MHz) allowing very fast operation.