In 1992 neurophysiologists  found a new type of cells in areas V1 and V2 of the monkey primary visual cortex, which they called grating cells. These cells respond vigorously to a grating pattern of appropriate orientation and periodicity. Three years later a computational model inspired by these findings was published . The study of this paper is to create a grating cell operator that has similar response profiles as monkey grating cells have. Three different databases containing a total of 338 real world images of textures are applied to the new operator to get better a insight to which natural patterns grating cells respond. Based on these images, our findings are that grating cells respond best to repetitive alternating patterns of a specific orientation. These patterns are in common human made structures, like buildings, fabrics, and tiles.