Discovery of piezoelectric effect
In 1880 two Frenchmen, the brothers Pierre and Jacques Curie, demonstrated that certain crystals have a remarkable property.
When you squeeze them an electrical voltage appears, almost as if a tiny, invisible battery suddenly appeared.
The Curie brothers showed that, among others, crystals of quartz, tourmaline and cane sugar have this property, which they called the piezoelectric effect, from the Greek piezein, meaning to squeeze or press.
The Curies knew nothing about the atomic models used today to explain this phenomenon - but they knew a lot about crystals. They expected certain crystals to show this effect, even before their experiments. For them it was just another way in which this weird, mysterious thing called electricity cropped up when you were working with crystals.
The next advance in the infant science of piezoelectricity came swiftly. In 1881 Lippman showed by mathematical calculations, based on fundamental principles of physics, that the opposite of what the Curies had demonstrated would also happen - if you applied voltage to those same crystals, they would be flattened slightly.
The Curies confirmed experimentally that this was the case, and henceforth scientists would speak of the direct piezoelectric effect.
The first practical application of piezoelectric devices, an ultrasonic submarine detector developed by the French during the First World War, triggered an explosion of interest.
A common application of piezoelectricity in cars is the tiny buzzers with their thin, metallic sound, which warn you if you have left your headlights on or forgotten to fasten your seat belt.