The properties of titin, a giant, structurally and mechanically complex filamentous protein were explored here by using single-molecule techniques. Fluorescently labeled titin molecules deposited on a glass substrate surface were directly visualized by using confocal microscopy. The molecules appeared as bright particles with a spatially distributed Gaussian fluorescence intensity profile. The physical dimensions of the space occupied by the 1-µm-long molecule on the surface are below the 0.25 µm resolution limit of the instrument used here, thereby directly demonstrating the flexible nature of the titin filament. The kinetics of titin's surface adsorption revealed that the process is governed by diffusion and the molecules are irreversibly bound to the substrate surface. From the kinetics data the molecule's translational diffusion constant was calculated.