(1)   The theory that describes strong interactions between quarks and gluons, quantum chromodynamics (QCD), has a coupling strength that is stronger in low energies, making it implausible to study low-energy particle phenomenology using perturbation theory. Lattice gauge theory is a rigorous non-perturbative tool to study strong interactions from first principles. I will give an overview of lattice QCD and its applications in particle and nuclear physics. Using the lattice approach to study other QCD-like theories will also be briefly discussed.

(2)   The advent of ground-based atmospheric and water Cherenkov gamma-ray detectors, as well as, the Compton and Fermi satellites has revolutionized our view of the TeV sky. Twenty years ago there was only one known TeV gamma-ray source, the Crab. Today there are well over 100 detected sources - steady and variable, point-like and diffuse. We have also made great strides studying Gamma Ray Bursts, the most energetic processes in the Universe. Most recently, we have even discovered that charged TeV cosmic rays have unexpected anisotropies in their arrival directions suggesting the existence of local cosmic ray sources. The next generation detectors, CTA, HAWC and, IceCube will undoubtedly give us a better understanding of these exciting phenomena and almost certainly reveal more surprises. In this talk, I will review some of these results and show results from the Milagro gamma ray observatory. In addition, I describe our next generation HAWC observatory currently under construction at high-altitude in Mexico.