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Electron energy loss spectroscopy (EELS) measures the spectral distribution of energy transferred from an incident electron beam into a specimen. In general, there are mainly two types of fundamental methods:
         i) Low energy beams reflected by solid surfaces, presenting the excitation spectrum from meV to eV. A representative technique is vibrational spectroscopy.
         ii) High energy beams transmitted through thin TEM films, presenting the inelastic scattering events in an energy range of eV to keV.

Electron monochromator [1] has improved the EELS energy resolution about 3-fold, to ~10 meV. At such high energy resolution, vibrational spectroscopy is available in the electron microscope [2]. As shown in the vibrational spectrum in Figure 2398, the different peaks can be assigned to different types of bonds and vibration modes.

[1] O. L. Krivanek et al., Microscopy 62 (2013) 3-21.
[2] O. L. Krivanek et al., Nature 514 (2014) 209-212.
[3] H. Cohen, P. Rez, T. Aoki, P.A. Crozier, N. Dellby, Z. Dellby, D. Gur, T.C. Lovejoy, K. March, M.C. Sarahan, S.G. Wolf and O. L. Krivanek, Hydrogen Analysis by Ultra-High Energy Resolution EELS, Microsc. Microanal. 21, 661, 2015.