POET (Polarimeters for Energetic Transients) represents a concept for a Small Explorer (SMEX) satellite mission, whose principal scientific goal is to understand the structure of GRB sources through sensitive X-ray and ?-ray polarization measurements. The payload consists of two wide field-of-view (FoV) instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2-15 keV and a high energy polarimeter (Gamma-Ray Polarimeter Experiment or GRAPE) that would measure polarization in the 60-500 keV energy range. The POET spacecraft provides a zenith-pointed platform for maximizing the exposure to deep space. Spacecraft rotation provides a means of effectively dealing with any residual systematic effects in the polarization response. POET provides sufficient sensitivity and sky coverage to measure statistically significant polarization (for polarization levels in excess of 20%) for 80 GRBs in a two-year mission. High energy polarization data would also be obtained for SGRs, solar flares, pulsars and other sources of astronomical interest.