Abstract　  

   Space gamma-ray astronomy was born here at MIT more than a half century ago. A few gamma-ray satellites operated since then, in particular the most recent Fermi Gammaray Space Telescope, have proved the great potential of probing a wealth of questions among the most important themes of astrophysics, cosmology, and fundamental physics. However, the low energy range of gamma rays is still poorly covered after decades. PANGU (the PAir-productioN Gamma-ray Unit) is a small astrophysics mission with wide field of view optimized for spectro-imaging, timing and polarization studies. It will map the gamma-ray sky at this crucial energy range with unprecedented spatial resolution.

   Unlike GeV photons which could only be detected above the atmosphere, observations of the Cosmic Microwave Background (CMB) have been achieved with much less costly ground-based telescopes at the South Pole and the Atacama desert in Chile. I'll describe a unique site located at the Tibet Plateau which opens the northern sky for future ground-based CMB telescopes, to search for signatures of inflation -- a period of accelerated expansion in the very early Universe and to probe the structure growth of our Universe.