Evolution of active region NOAA 12597 on 2016 September 24 based on HMI continuum images with a FOV of 150′′ × 80′′. Major tick marks are placed at 10′′-intervals. The images were displayed at two-hour intervals starting at 01:00 UT. The abbreviations in the 09:00 UT panel indicate the leading spot P₁, the trailing pores N₁ and N₂, the central negative pore N₃, and the leading and trailing pores p₁ and n₁ of the emerging active region.