A PhD student proposed that matter itself moves like a wave

In 1924, Louis de Broglie suggested that if light can behave like a particle, particles like electrons might behave like waves too. His examiners were baffled enough to consult Einstein, who called it brilliant. Three years later, electrons were shown to diffract exactly as his equations predicted.

— Louis de Broglie, Recherches sur la théorie des quanta — PhD thesis, 1924