A sample of late M-type stars, illustrating the characteristics used for classification. The depth of the TiO bandhead at 8860 Å is expected to depend linearly with T_eff. The 8620 Å DIB is blended with the VO bandhead at 8624 Å, only visible in stars later than M6. The spectrum of the M7.5 I RSG MY Cep, in the open cluster NGC 7419, is shown for comparison. All the spectra have been normalised in the same, rather arbitrary, way.