The zero point energy of a system in a potential well is reviewed as a concept, with some history of the development behind it, and a discussion is given of how it can be detected experimentally from the electronic-vibrational spectrum of molecules with different isotopes (isotope effect). Also discussed is how the zero point oscillations of crystal lattice atoms show up in the diffraction of X-rays and neutrons from crystals and in the temperature dependence of the Mössbauer effect probability. Other topics include measuring zero point oscillations of water molecules in a nanotube to determine the form of the potential energy of the system; the role of zero point oscillations in the dynamics of electrons in semiconductors, and experiments on the optical cooling and quantum behavior of mechanical oscillators.