Recent observations of the Galactic plane with wide-field air shower gamma-ray observatories have revealed emitters producing gamma rays at energies reaching into the multi-hundreds of TeV range, challenging our previous understanding based on traditional wavelengths. This talk will explore these newly identified sources, including X-ray binaries, supernova remnants, and star-forming regions, using data from the HAWC Observatory and the Fermi Telescope. We will also discuss particle accelerators identified through neutrino observations, demonstrating that they differ significantly from the aforementioned sources and could be gamma-ray-obscured. Finally, we will discuss theoretical interpretations that provide insight into these findings and their implications for high-energy astrophysical processes.