My research involves the study of dust in various astrophysical environments: circumstellar, interstellar and extragalactic. I am studying how dust grain properties change from quiescent cloud to star-forming cloud to circumstellar environments.With my collaborators, I am modeling dust on microscopic and macroscopic scales to determine the role of dust in the energy budget of these various environments. We use extinction, polarization, abundance and spectroscopic observations from the UV to the IR for the same sightlines obtained from Hubble and Spitzer Space Telescopes as well as other space- and ground-based telescopes. The goal is to produce a unified model of dust which will satisfy observational constraints from all wavelengths (UV to IR) in these different environments using the DDA and MEM codes. To this end we are investigating Radiative Transfer in circumstellar, star formation and extragalactic environments. The capabilities of our Monte Carlo codes include, scattering, radiative equilibrium solutions, emission from PAHs, and scattering from aligned grains. These codes produce spectra, images, and polarization (images and spectra) for comparison with observations.