cores with the Infrared Array Camera (IRAC; Fazio et al. 2004) and the Multiband Imaging Photometer (MIPS; Rieke et al. 2004), providing images ranging from 3.6 to 70 $\mu$m. *Spitzer* is much more sensitive than previous space infrared missions, providing an ability to detect fainter, less-luminous sources than was possible with previous infrared surveys. In fact, *Spitzer* c2d observations have shown that several cores believed to be starless (containing no protostars) actually harbor Very Low Luminosity Objects (VeLLOs) with internal luminosities[^1] $L_{int} \leq 0.1$  (e.g. Young et al. 2004, Di Francesco et al. 2006). Infrared images can reveal a wealth of information about the internal sources embedded in dense cores, but the infrared alone does not tell the whole story.

To fully understand the process of low-mass star formation and the nature of embedded protostars, one must understand the details of the dusty envelopes in which they are embedded. Even though these envelopes are usually quite cold ($\sim$ 10 K; e.g. Di Francesco et al. 2006), except for the inner regions where they are heated by the internal source, their thermal emission can easily be detected at submillimeter and millimeter wavelengths. Complementary surveys are obtaining continuum observations at 850 $\mu$m 