WE PROPOSE TO STUDY THE ELEMENTAL AND ISOTOPIC COMPOSITION OF THE OLDEST MATERIAL IN THE SOLAR SYSTEM, PRESOLAR GRAINS AND METEORITIC NANODIAMONDS, TO IMPROVE OUR UNDERSTANDING OF THE ORIGIN OF OUR SOLAR SYSTEM. OUR FIRST GOAL IS TO START TO ESTABLISH A PRESOLAR CHRONOLOGY BY DETERMINING INTERSTELLAR RESIDENCE TIMES OF LARGE PRESOLAR SILICON CARBIDE (SIC) GRAINS BY PRESOLAR COSMIC-RAY EXPOSURE AGE DATING WITH NOBLE GAS MASS SPECTROMETRY AND SECONDARY ION MASS SPECTROMETRY (NANOSIMS) (TASK 1). AGES FROM PRESOLAR GRAIN HAVE THE POTENTIAL TO PROVIDE CRUCIAL INFORMATION TOWARDS A BETTER UNDERSTANDING OF PROCESSES IN THE INTERSTELLAR MEDIUM AND THE LATE EVOLUTION OF OUR GALAXY. OUR SECOND GOAL IS TO FULLY ESTABLISH ATOM-PROBE TOMOGRAPHY (APT) IN ISOTOPE COSMOCHEMISTRY BY CORRECTING FOR REMAINING TECHNICAL BIASES. THIS BUILDS ONTO OUR PIONEERING EFFORT IN DEVELOPING APT FOR COSMOCHEMISTRY THAT WE STARTED FOUR YEARS AGO. OUR IMMEDIATE SCIENTIFIC OBJECTIVE IS TO HELP ANSWERING THE 26-YEAR-OLD QUESTION OF THE ORIGIN OF METEORITIC NANODIAMONDS THROUGH ANALYSES OF THE CARBON ISOTOPIC COMPOSITION OF SINGLE GRAINS (TASK 2). APT IS THE ONLY TECHNIQUE WITH THE REQUIRED SPATIAL RESOLUTION AND SENSITIVITY TO ANALYZE CARBON ISOTOPES IN INDIVIDUAL NANODIAMONDS. IN ADDITION, WE WILL APPLY APT TO THE ANALYSIS OF OTHER TYPES OF PRESOLAR GRAINS, SPECIFICALLY PRESOLAR CR-ANOMALOUS NANO-OXIDES (TASK 3). THESE SAMPLES ARE TOO SMALL FOR CLEAN, UNMIXED ISOTOPE ANALYSIS WITH OTHER TECHNIQUES SUCH AS NANOSIMS. APT OF SUCH NANO-OXIDES HAS THE POTENTIAL TO PROVIDE NEW INFORMATION ON THE NUCLEOSYNTHETIC SOURCES AND THE EARLY SOLAR SYSTEM. APT HAS THE POTENTIAL TO LAUNCH THE FIELD OF ISOTOPE COSMOCHEMISTRY INTO PREVIOUSLY UNEXPLORED TERRITORY WITH IN IMPROVEMENT OF SPATIAL RESOLUTION OF ABOUT TWO ORDERS OF MAGNITUDE COMPARED TO NANOSIMS.