['It has been reported that both chemical and physical surface patterns influence cellular behaviors, such as cell alignment and elongation. However, it still remains unclear how actin filament and microtubules (MTs) differentially respond to these patterns.', 'We examined the effects of chemical and physical patterns on cell elongation and alignment by observing actin filament and MTs of retinal pigment epithelium-1(RPE-1) cells, which were cultured on either fibronectin (FN)-line pattern (line width and spacing: 1\xa0μm) or FN-coated 1\xa0μm gratings with two different depths (0.35 or 1\xa0μm). On the surface with either FN-line pattern or micrograting structure, the cell aspect ratios were at least two times higher than those on the surface with no pattern. Cell elongation on the gratings depended on the depth of the gratings. Cell elongation and alignment on both FN-line pattern and 1\xa0μm gratings with 0.35\xa0μm depth were perturbed either by inhibition of actin polymerization or MT depletion, while cell elongation and alignment on 1\xa0μm gratings with 1\xa0μm depth were perturbed only by MT depletion.'] Does contribution of actin filaments and microtubules to cell elongation and alignment depend on the grating depth of microgratings?