Atomic Force Microscopy(AFM)has been widely used in various research fields since its invention in 1980s.The state-of-the-art non-contact AFM(NC-AFM),enquired with high Q-factor tuning fork sensors,substantially improves the imaging resolution to the interatomic scale.In this talk,I will present a systematical density functional theory study on the free standing and adsorbed bis(para-pyridyl)acetylene(BPPA)tetramer on Au(111)surface which sheds new lights on understanding the mechanism of NC-AFM imaging and show the potential for using NC-AFM to measure spatially resolved electronic interactions of materials under external pressure [1].