Kelvin probe force microscopy (KPFM), an electrostatic force microscopy (EFM) technique, is widely applied to study electrical surface properties of various conductive or semiconductive samples. KPFM provides quantitative results of the local surface potential distribution or, if calibrated, the work function of the sample. For that, KPFM uses the same basic experimantel configuration as EFM. The cantilever is mechanically excited while an AC voltage is applied to the tip and sample. Meanwhile, a second lock-in amplifier compensates the potential difference between sample and cantilever by applying an addtional DC bias. Thus, the feedback signal can be used to create a surface potential map. KPFM is widely used in both research and industry to image changes in work function for various applications as polymer compounds or electronic devices like solar cells. In this webinar, we will show the principles and applications of KPFM on Park FX40 - the automatic AFM.