Major components of the two STEM columns dedicated to EELS studies presently in operation in Orsay : (left) the VG HB501 received in 1980, (right) the NION Chromatem received in 2018. With respect to the simple VG microscope, the NION one incorporates three new major electron optical components: a monochromator, an aberration corrector in the probe forming optics, an aberration-corrected EELS spectrometer and associated parallel EELS detector, the schematic cross section of the monochromated NION column is extracted from [20]. Associated with these figures are characteristics of key parameters of the probe (intensity, lateral size, energy width) for the two instruments.