WE PROPOSE TO PERFORM A SURVEY FOR BROWN DWARFS AT PLANETARY MASSES (<10 JUPITER MASSES) IN THE NEAREST AND RICHEST STAR-FORMING CLUSTERS AND ASSOCIATIONS (<10 MYR D=150-300 PC). CANDIDATE BROWN DWARFS WILL BE IDENTIFIED THROUGH PHOTOMETRY AND PROPER MOTIONS MEASURED WITH WIDE-FIELD IMAGING SURVEYS (UKIDSS PAN-STARRS1) ARCHIVAL IMAGES FROM THE SPITZER SPACE TELESCOPE NEW IMAGES FROM THE JAMES WEBB SPACE TELESCOPE (JWST) AND NEW AND ARCHIVAL IMAGES FROM GROUND-BASED TELESCOPES. THESE CANDIDATES WILL BE OBSERVED WITH NEAR-INFRARED SPECTROSCOPY TO CONFIRM THEIR YOUTH (AND HENCE CLUSTER MEMBERSHIP) AND COOL NATURE. THROUGH THIS SURVEY WE SEEK TO OBTAIN SAMPLES OF YOUNG PLANETARY-MASS BROWN DWARFS THAT ARE AS LARGE AS POSSIBLE (>50) AND THAT REACH THE LOWEST POSSIBLE MASSES (~1 JUPITER MASS). THESE OBJECTS CAN THEN BE USED TO IMPROVE OUR UNDERSTANDING OF THE FORMATION OF PLANETS IN THE FOLLOWING WAYS: 1) THE LOWEST MASS AT WHICH FREE-FLOATING BROWN DWARFS ARE ABLE TO FORM PROVIDES A CONSTRAINT ON THE POSSIBLE FORMATION MECHANISMS FOR PLANETARY-MASS COMPANIONS. IF FREE-FLOATING BROWN DWARFS FORM DOWN TO A GIVEN MASS (E.G. 1 JUPITER MASS) THEN IT IS PLAUSIBLE THAT SOME COMPANIONS AT SIMILAR MASSES HAVE FORMED LIKE BINARY STARS (E.G. CLOUD CORE FRAGMENTATION). 2) IT HAS BEEN PREVIOUSLY PROPOSED THAT MID-INFRARED SPECTRA MAY CONTAIN SIGNATURES THAT INDICATE WHETHER A SUBSTELLAR OBJECT HAS FORMED VIA CORE ACCRETION WITHIN A CIRCUMSTELLAR DISK (I.E. A PLANET) OR THROUGH THE COLLAPSE OF A MOLECULAR CLOUD CORE (I.E. A BROWN DWARF). FUTURE STUDIES CAN VERIFY THE PRESENCE OF SUCH SIGNATURES THROUGH THE COMPARISON OF SPECTRA (ESPECIALLY FROM JWST) OF FREEFLOATING BROWN DWARFS FOUND IN OUR SURVEY AND PLANETARY COMPANIONS FROM DIRECT IMAGING SURVEYS. 3) FUTURE STUDIES CAN USE JWST TO OBTAIN MID-INFRARED PHOTOMETRY FOR THE PLANETARY-MASS BROWN DWARFS FOUND THROUGH THIS PROPOSAL WHICH CAN DETERMINE IF THEY HARBOR CIRCUMSTELLAR DISKS. IN THIS WAY THOSE STUDIES CAN IDENTIFY THE LOWEST MASS AT WHICH BROWN DWARFS HAVE THE RAW MATERIALS FOR MAKING PLANETS (I.E. WHAT ARE THE SMALLEST "STARS" THAT COULD POTENTIALLY HARBOR PLANETS?).