Colloidal Quantum Dots (CQD) have been historically studied in the visible region, but they have the potential to transform infrared technologies by providing much lower processing cost and possibly better performance than traditional HgCdTe of InSb bulk detectors. CQDs can display strong infrared electronic transitions using either interband or intraband transitions. HgTe is a semi metal with a light electron such that nanoparticles of sizes between 20 and 6 nm have absorption edges from 12 to 2 microns. Thus, HgTe CQDs cover all the mid-infrared. As synthesized, HgTe CQDs are nearly intrinsic, films readily exhibit photoconductance from room temperature to low temperatures, and photovoltaic structures achieve Background Limited Performance (BLIP). The main challenge is to raise the operation temperature which requires to reduce non-radiative losses and to control accurately the doping, both stemming from surface chemistry. The other approach to the mid-infrared is to use the intraband transitions of doped quantum dots. HgTe and HgS are two systems that show stable n-doping in ambient conditions and that have been demonstrated as photoconductors. Potential advantages of the intraband approach are the elimination of Auger processes, the increased absorption per unit length, a narrower photodetection spectral range, and the possibility of using a wider range of starting materials, including wide band gap visible transparent semiconductors. The talk will review the progress and challenges of this new material approach to infrared technology.