Adhesion phenomenon is more significant for smaller objects, because adhesional force is proportional to size of the objects while gravitational force is proportional to the third power of it. For the purpose of micro-assembly, theoretical understanding is required for the Adhesion phenomenon. Author has developed a force measurement system in an ultra-high vacuum chamber of Auger electron spectroscope. The force between arbitrary combination of materials can be measured at a pressure less than 100 nPa after and before Ar ion sputtering and chemical analysis for several atomic layers of the surface by electron spectroscopy. The results are successfully interpreted with a theory of contact mechanics. Since surface energy is quite important in the interpretation, electronic theory is used to evaluate the surface energy, and molecular statistic calculation with modified embedded atom method (EAM) inter-atomic potential series. In the manipulation of small objects, the adhesion force is always attractive. Repulsive force is essential for the manipulation. It can be generated by Coulomb interaction. The voltage required for detachment is theoretically analyzed and the effect of boundary conditions on the detachment is obtained. The possibility and limitations of micro-manipulation using both the adhesion phenomenon and Coulomb interaction are theoretically clarified, and discussed with experiments.