Examples of two solar ARs, in terms of their photospheric continuum intensity images (a, b), LOS magnetograms (c, d) and EUV coronal images at 19.3 nm (e, f). Both active regions were observed on 5 September 2017 at around 12:01 UT. Of them, NOAA AR 12673 (left column) was intensely eruptive, giving the largest eruptive flares since January 2005, while NOAA AR 12674 (right column) did not host any major flares. Images (a–d) have been acquired by HMI, while images (e, f) by AIA, both onboard the SDO mission.