The ferroelectric effect was first observed by Valasek in 1921, in the Rochelle salt. This has molecular formula KNaC4H4O6·4H2O. The effect was then not considered for some time, and it wasn't until a few decades ago that they came into great use. Nowadays, ferroelectric materials are used widely, mainly in memory applications. This TLP will show how the ferroelectric effect arises, and how it is usefully used.