Beginning with a brief history of the discovery of piezoelectricity, this chapter focuses on a clear description of the direct and reciprocal piezoelectric effects. The starting point is the macroscopic quartz crystal in its low-temperature modification, also known as \(\upalpha \) -quartz, a stable modification of silica and the second most abundant mineral in the Earth’s crust. The terms crystallographic main axis and polar axes are introduced and clearly illustrated. The latter are essential for further understanding of the direct and reciprocal piezoelectric effect. The generation of piezoelectricity at the macroscopic level is then demonstrated using the example of a hexagonal quartz prism subjected to mechanical pressure. The physical explanation of the phenomenon at the prism is based on the structural composition of \(\upalpha \) -quartz and the chemical bonding ratios at the molecular level. The specific spatial networking of the structure-forming coordination polyhedra of \(\upalpha \) -quartz and its mesomeric boundary structures leads to its six-sided, three-dimensional structural cell. From this, a simplified form of the structural cell can be derived, which is ultimately used to clearly describe the direct and reciprocal piezoelectric effects—with the simultaneous introduction of the electrical polarisation associated with both effects.