The field of nonlinear dielectric effects started with Debye's work on dielectric saturation. The signature of this effect is a reduction of the dielectric constant, ϵ, with increasing electric field. The work of Piekara added the so-called "chemical effect", an increase in ϵ that originates from an equilibrium of two species with different dipole moments. More recently, dielectric hole burning and similar techniques based on high ac fields demonstrated that the energy absorbed from a field can accelerate dynamics, even for isothermal conditions. For strong static (dc) fields, the dynamics of polar liquids can become slower relative to the field free case. Thus, depending of the type of field applied, these reversible field effects can lead to amplitudes increasing or decreasing, and to the loss spectrum being shifted to the left or right along the logarithmic frequency scale. Additionally, crystallization outcomes can be modified by static fields of moderate amplitude.