THE DEVELOPMENT OF A COMPREHENSIVE UNDERSTANDING THE PHYSICS THAT LED TO THE FORMATION OF FIRST STARS AND GALAXIES IS A CHALLENGING BUT FUNDAMENTAL GOAL OF EXTRAGALACTIC ASTROPHYSICS. THOUGH A GREAT DEAL HAS BEEN LEARNED IN THE PAST TWO DECADES MANY KEY QUESTIONS REMAIN. FIRST HOW AND WHEN DID THE FIRST UV-BRIGHT STARS THAT RE-IONIZED THE UNIVERSE FORM FROM PRISTINE PRIMORDIAL GAS? SECOND WHAT IS HISTORY OF STELLAR DUST AND METAL BUILD-UP DURING RE-IONIZATION? THIRD WHAT IS THE CONTRIBUTION OF QUASARS TO THE RE-IONIZATION HISTORY OF THE UNIVERSE? OVER THE NEXT DECADE MULTI-WAVELENGTH OBSERVATIONS OF THE FIRST GALAXIES AND THE EARLY INTERGALACTIC MEDIUM WILL YIELD SIGNIFICANT NEW CLUES IN OUR QUEST TO DEVELOP A FUNDAMENTAL UNDERSTANDING OF THE PHYSICS OF THE EPOCH OF RE-IONIZATION (EOR). THE NEW WORLDS NEW HORIZONS (NWNH) REPORT IDENTIFIED THE STUDY OF RE-IONIZATION AS A TOPIC RIPE FOR FUNDAMENTAL BREAKTHROUGHS IN THE 2010-2020 DECADE. WE EXPECT THESE DEVELOPMENTS TO CONTINUE INTO 2020-2030 THANKS TO EXPECTED OBSERVATIONAL AND SURVEY CAPABILITIES OF BOTH JWST AND WFIRST. UNFORTUNATELY JWST COSMOLOGICAL FIELDS WILL BE LIMITED TO A HANDFUL OF DEEP FIELDS WITH A TOTAL AREA OF SEVERAL HUNDRED ARCMIN2. WHILE WFIRST WILL BE CAPABLE OF WIDE AREA SURVEYS LACK OF SPECTROSCOPIC CAPABILITY BEYOND 2 M LIMITS DETECTION OF H AT Z>2 AND THE SELECTION OF Z>6 GALAXIES WILL BE LIMITED TO PHOTOMETRIC DATA. THUS BOTH JWST AND WFIRST ARE NOT DEFINITIVE MISSIONS TO COMPLETE OUR UNDERSTANDING OF RE-IONIZATION INCLUDING ANSWERS TO CRITICAL QUESTIONS ON HOW AND WHEN GALAXIES AND QUASARS FIRST FORMED THE HISTORY OF METAL BUILD-UP AND THE HISTORY AND TOPOLOGY OF RE-IONIZATION AMONG OTHER QUESTIONS. A PROBE CLASS MISSION OPTIMIZED FOR RE-IONIZATION STUDIES WILL BE THE FIRST NECESSARY STEP ON A PATH TO ADVANCE OUR KNOWLEDGE. SUCH A MISSION WILL NEED TO EXPAND BOTH IMAGING AND SPECTROSCOPIC CAPABILITIES OVER THE EXPECTATIONS FROM JWST AND WFIRST. COSMIC DAWN INTENSITY MAPPER (CDIM) IS 1.5M-CLASS INFRARED TELESCOPE CAPABLE OF THREE-DIMENSIONAL SPECTRO-IMAGING OBSERVATIONS OVER THE WAVELENGTH RANGE OF 0.75 TO 7.5 MICRONS AT A SPECTRAL RESOLVING POWER OF 500. THIS WILL BE ACHIEVED WITH LINEAR VARIABLE FILTERS (LVFS) SITTING ON TOP OF A FOCAL PLANE OF 36 20482 DETECTORS. THE FIELD-OF-VIEW (FOV) OF CDIM WILL BE 10 SQ. DEG INSTANTANEOUSLY. THE SURVEY STRATEGY USING SPACECRAFT OPERATIONS FOLLOWING A SHIFT AND STARE MODE WILL RESULT IN 1360 INDEPENDENT NARROW-BAND SPECTRAL IMAGES OF THE SKY ON A GIVEN LOCATION. CURRENTLY PRIORITIZED SCIENCE PROGRAMS TAKING OVER THREE-YEARS OF A FIVE-YEAR MISSION WILL BE ACCOMPLISHED WITH A TWO-TIERED WEDDING-CAKE SURVEY WITH THE SHALLOWEST SPANNING CLOSE TO 300 SQ. DEG AND THE DEEPEST TIER OF ABOUT 25 SQ. DEG. THE REMAINING TWO-YEARS COULD BE USED FOR ADDITIONAL SURVEY PROGRAMS (THE WIDE TIER CAN BE EXPANDED TO 1000 SQ. DEG) OR FOR USE BY THE ASTRONOMICAL COMMUNITY THROUGH A GENERAL OBSERVING (GO) CAMPAIGN. CDIM SURVEY DATA WILL ALLOW US TO (I) DETERMINE SPECTROSCOPIC REDSHIFTS OF WFIRST-DETECTED LYMAN-BREAK GALAXIES (LBGS) OUT TO A REDSHIFT OF 10; (II) ESTABLISH THE ENVIRONMENTAL DEPENDENCE OF STAR-FORMATION DURING RE-IONIZATION THROUGH CLUSTERING AND OTHER ENVIRONMENTAL MEASUREMENTS; (III) ESTABLISH THE METAL ABUNDANCE OF FIRST-LIGHT GALAXIES DURING RE-IONIZATION OVER TWO DECADES OF STELLAR MASS BY SPECTRALLY SEPARATING NII FROM H AND DETECTING BOTH H AND OIII. IV) MEASURE 3D INTENSITY FLUCTUATIONS DURING RE-IONIZATION IN BOTH LY AND H; AND (V) COMBINE INTENSITY FLUCTUATIONS WITH 21-CM DATA TO ESTABLISH THE TOPOLOGY OF RE-IONIZATION BUBBLES. THE ASSEMBLED TEAM IS WELL QUALIFIED TO DEVELOP THE PROPOSED 3D SPECTROSCOPY IMAGER. WE PROPOSE A TEAM-X SESSION AT JPL. OUR PRIMARY OBJECTIVE IS TO ESTABLISH A LOW-COST PROBE CLASS MISSION AS THE PREMIER VEHICLE FOR A FUNDAMENTAL BREAKTHROUGH IN OUR KNOWLEDGE RELATED TO RE-IONIZATION.