(a) Schematic of the formation of a downward polarized (P[00[macr1]]) region within an upward polarized (P) film cross-section by the application of a local electric field via a surface probe. The polarization results from the offset of the oxygen octahedra to the Zr/Ti and Pb cations forming an electric dipole, which reorients upon switching. (b) A dark-field TEM image of alternating P[00[macr1]] and P domains produced in a 100-nm PZT film by in situ electrical switching. Scale bar, 100 nm. (c) A high-resolution high-angle annular dark-field image of the domain wall bordering a switched domain and the corresponding map of the polarization direction determined by the relative offset of the Zr/Ti atoms, confirming a 180° rotation. Scale bar, 1 nm.