OUR PROPOSAL `EXPLORING THE VARIABILITY OF ULTRACOOL DWARFS WITH TESS' WILL USE DATA FROM THE TRANSITING EXOPLANET SURVEY SATELLITE TO CONDUCT THE FIRST SYSTEMATIC AND STATISTICALLY ROBUST STUDY OF VARIABILITY IN VERY-LOW MASS STARS AND BROWN DWARFS AS IT RELATES TO ATMOSPHERIC METEOROLOGY AND MAGNETIC ACTIVITY. WE WILL EXAMINE THE LIGHT CURVES GENERATED FROM TESS 30 MIN DATA FOR SEVERAL HUNDREDS OF THESE OBJECTS TO CHARACTERIZE BRIGHTNESS MODULATIONS FEATURE MODULATED ROTATIONAL PERIODS AND FLARING RATES. WE WILL ALSO TARGET A SELECT SAMPLE OF BRIGHT NEARBY TARGETS FOR 2 MIN CADENCE OBSERVATIONS TO ANALYZE FLARE PROFILE STRUCTURE AND STOCHASTIC/SHORT TIMESCALE VARIABILITY. THESE OBSERVATIONS WILL ALLOW A DETAILED STUDY ON THE NATURE OF THE ATMOSPHERIC STRUCTURAL AND ROTATIONAL CHANGES AT THE END OF THE STELLAR MAIN SEQUENCE.USING TESS LIGHT CURVES FOR OUR SAMPLE OF TARGETS WE WILL APPLY PERIODOGRAM METHODS AND PHASE DISPERSION MINIMIZATION TO LOOK FOR PERIODIC AND QUASI-PERIODIC VARIABILITY AND MEASURE ITS PERIODICITY WITH BY EYE VERIFICATION. WE WILL USE AN AUTOMATED FLARE FINDING ROUTINE TO LOOK FOR FLARES IN ALL OUR LIGHT CURVES AND USE A FLARE INJECTION ANALYSIS TO DETERMINE OUR TESS FLARE SENSITIVITY FOR EACH TARGET. ONCE IDENTIFIED WE WILL MEASURE THE FLARE ENERGIES OF ALL OBSERVED FLARES AND CHARACTERIZE THE FLARE SHAPES BASED ON ESTABLISHED IMPULSIVE FLARE TEMPLATES. WE WILL FURTHER USE THE ACCUMULATED FLARE DATA TO CONSTRUCT FLARE FREQUENCY DISTRIBUTIONS ACROSS OUR FULL TARGET SAMPLE. OUR ANALYSIS OF THE TESS LIGHT CURVES WILL YIELD THE LARGEST NUMBER OF ROTATION PERIOD MEASUREMENTS FOR VERY-LOW MASS STARS AND BROWN DWARFS FREQUENCY DISTRIBUTIONS AND FLARE SHAPE PARAMETERS FOR THE COOLEST NEARBY OBJECTS AND AN ASSESSMENT OF THE BROADBAND LIGHT CURVE MORPHOLOGIES AND EVOLUTION TIMESCALES INCLUDING POTENTIAL WEATHER PHENOMENA. THESE MEASUREMENTS CAN THEN BE RELATED TO THE PHYSICAL STELLAR PROPERTIES AND OTHER EXISTING MEASUREMENTS OF MAGNETIC ACTIVITY. THIS PROPOSAL ENHANCES THE SCIENCE RETURN OF THE TESS MISSION THROUGH AN IN-DEPTH STUDY OF THE ASTROPHYSICS GOVERNING THESE PROCESSES IN VERY-LOW MASS STARS AND BROWN DWARFS. FURTHERMORE UNDERSTANDING THESE ATMOSPHERIC AND MAGNETIC PROPERTIES IS A CRUCIAL INGREDIENT FOR ASSESSING THE IMPACT OF STELLAR ACTIVITY LIKE FLARES ON EXOPLANETARY ATMOSPHERES ORBITING THESE SYSTEMS AND DETERMINING THEIR PROSPECTS FOR HABITABILITY. COLLECTIVELY THESE EFFORTS EXPAND OUR KNOWLEDGE OF STELLAR ASTROPHYSICS AND PROBE THE ABILITY OF DIVERSE STELLAR SYSTEMS TO POTENTIALLY DEVELOP LIFE.