If dark matter is made of particles governed by weak-scale physics, they may annihilate or decay to leave observable signatures in high-energy gamma-ray sky. In addition, any charged particles produced by the same process will also give low-frequency photons through successive electromagnetic interactions. Plenty of data from modern astrophysical measurements of various wavelengths, especially gamma rays, enabled new analysis techniques to search for these dark matter signatures with an

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... ented sensitivities. Since it is very likely that signatures of dark matter annihilation or decay is hidden in the gamma-ray data, one should fully utilize all available data including: (1) energy spectrum of all wavelengths ranging from radio to very-high-energy gamma rays; (2) spatial clustering probed with the angular power spectrum of the gamma-ray background; (3) cross correlation between the gamma-ray distribution with nearby galaxy catalogs; and (4) gamma-ray-flux distribution. I will review recent theoretical and observational developments in all these aspects, and discuss prospects for the future towards discovery of dark matter as an elementary particle in physics beyond the standard model.