Liquid-phase adsorption process of Beta-picoline molecules on a (010) surface of a natural zeolite stilbite was observed by atomic force microscopy (AFM). Initially, the surface was covered with excess multilayer beta-picoline molecules. Removal of this excess layer by AFM scanning exposed a possible random-adsorbed monolayer phase. A well-ordered two-dimensional quasihexagonal phase developed slowly, with an estimated rate of similar to 6 nm/min. The 2D unit cell dimension of the latter ordered phase was 0.55 +/- 0.04 nm. The ordered phase is incommensurate with the substrate surface, although one of the 2D lattice unit vectors of the adsorbed phase makes an angle of similar to 50 degrees and similar to 100 degrees with respect to the a and c axes of the substrate (010) plane, respectively. From the position of the methyl group in the P-picoline molecule it is estimated that the molecules are adsorbed on the surface with their C-N bond parallel to the surface.