Nanowires (NWs) have the potential to enhance the speed and efficiency of optoelectronic devices; however, there is much unknown about the physics of these colloidal nanowires. Time-resolved (TR) spectroscopy provides useful information about these nanostructures. In the present study we performed TR spectroscopy at low temperatures (~10K) in order to study the emission properties of single colloidal CdSe nanowires (NWs) with diameter ~20 nm. A streak camera with resolution up to 8 picoseconds (pulse width) was used with a micro photoluminescence (ÁPL) setup to achieve micron spatial resolution measurements on several individual nanowires. We excited the NW samples with the second harmonic of a Ti-sapphire laser (wavelength at 400 nm, pulse frequency of 76 MHz) with a power density reaching the sample that can range from 100 W/cm2 to 25 kW/cm2. We also measured ÁPL spectra with an 80x, NA = 0.75 micro objective using the pulsed laser. Wide field luminescent images taken with the micro-objective verified that individual nanowires are measured. Low temperature TR spectroscopy of single nanowires shows a red-shift as a function of time which increases with power. At the largest pump powers (25kW/cm2) the spectra peak shifts ~20 meV within 500 psec. The shift is reduced but observable at lower pump powers, e.g., 1.4 meV in 500 psec for 200 W/cm2. In addition to the peak energy shift, the spectra half-width also decreases with time and pump power. At large pump powers the spectra emission range (FWHM) decreases ~40 meV in 500 psec. The peak energy shift as a function of time suggests that excitons populate many discrete localized states ranging in energy. At low temperature excitons are prevented tunneling to lower states before they recombine . We believe that these states come from traps in the nanowire. The larger power densities create more excitons that fill more traps of various energy levels; this causes the largest energy shift in the emission. Work was supported by the National Science Foundation, NSF-NIRT grant No. ECS-06 09249. We are greatful to, Dr. M. Kuno, Chemistry Department, University of Notre Dame, for the NW samples.  J.J. Glennon, R. Tang, W. E. Buhro, and R. A. Loomis. Phys. Rev. B 80 081303(R) 2009.