O-M and luminosity classes I-V. They also summarize the considerable body of work directed toward K–band spectroscopy in the last decade.

While in many situations, the K–band will be the wavelength selection of choice for spectroscopic studies of highly obscured or very cool objects, the presence of circumstellar dust ($T_{vap} < 2000 K$; Pollack et al. 1994) often results in significant excess continuum emission longward of $2~\mu$m. This continuum excess is commonly found in two important classes of objects: young stars with circumstellar disks (e.g. Meyer, Calvet, & Hillenbrand, 1997) and evolved stars with extensive envelopes from mass-loss (e.g. Le Bertre 1997). Near–infrared excess due to warm dust can also complicate spectroscopic studies of composite stellar systems aimed at discerning the stellar populations of other galaxies (e.g. Schinnerer et al. 1997). Continuum excess longward of $2~\mu$m will weaken or even render invisible the photospheric features in the K–band, while the photosphere will dominate at shorter wavelengths. In such a situation, near infrared spectra shortward of 2 $\mu$m will be required to see the stellar photosphere too obscured to be detected optically. To date, there has been relatively little work in the H–band (1.55–1.75 $\mu$m). Recent publications include: i) observations of 