The mechanism that facilitates polarization reorientation in KH2PO4 (KDP) was investigated using operando single-crystal neutron diffraction.Diffraction data were measured from a KDP single crystal during the application of alternating electric fields and were then binned into 40 increments to enable field-dependent single-crystal structure refinements.The field-dependent structures are compared with an as-grown crystal to determine how the lattice and atomic sites Football - Shoes - Junior evolve in response to the applied electric fields.These analyses provide evidence that the COLLOIDAL SILICEA reorientation of the macroscopic polarization is facilitated through a cooperative change in hydrogen bonding, which results in the reversal of the spontaneous dipole.In addition, a decrease in secondary extinction near the coercive field indicates that the inversion of the macroscopic polarization is achieved through the nucleation and subsequent growth of new domains.