Nearest distance between our galaxy sample and the SDSS galaxies. We search the SDSS galaxies with the velocity range from −500 to 500 km s⁻¹. We also roughly estimate the distance that may tidally affect our galaxy sample and show the results by the open circles. All of the nearest SDSS galaxies are still beyond the tidally affected distance. So, we conclude the origin of the “inside-out” or “outside-in” growth mode is more likely a result of secular evolution rather than the affection of the environment.