ONE OF OUR DEEPEST WINDOWS INTO THE UNIVERSE AT FAR-INFRARED (FIR) WAVELENGTHS BETWEEN 70 AND 500 MICRONS IS IN THE CANDELS/3DHST EXTRAGALACTIC FIELDS OWING TO A HUGE INVESTMENT OF THE SPITZER AND HERSCHEL SPACE OBSERVATORY RESOURCES. WHILE PUBLIC FIRSELECTED CATALOGS EXIST FOR ALMOST ALL HERSCHEL SURVEYS IN THESE FIELDS SIMPLE CROSS-MATCHING WITH ULTRAVIOLET (UV) TO NEAR-INFRARED (NIR) CATALOGS WILL NOT YIELD ROBUST PHOTOMETRY DUE TO SEVERE BLENDING ISSUES CAUSED BY THE LOW-RESOLUTION NATURE OF THE DATA. INSTEAD "FORCED PHOTOMETRY" WHICH USES SOURCE POSITIONS AND LIGHT PROFILES FROM A HIGHER RESOLUTION PRIOR TO DEFINE THE FIR SOURCES TO BE MEASURED IDENTIFIES ROUGHLY 50% MORE FIR-BRIGHT GALAXIES AND ENABLES AN ANALYSIS AT FAINT MAGNITUDES THAT IS OTHERWISE IMPOSSIBLE. HERE WE PROPOSE THE 3D-HERSCHEL LEGACY PROGRAM WHICH WILL PRODUCE THE FIRST COMPREHENSIVE MULTI-WAVELENGTH (0.3-500 MICRON) PHOTOMETRIC CATALOGS IN ALL FIVE CANDELS FIELDS BY BUILDING ON OUR EXISTING 3D-HST PHOTOMETRIC CATALOGS BY ADDING FIR FORCED PHOTOMETRY.