Gwenael Giacinti is a T. D. Lee Fellow at the Tsung-Dao Lee Institute, and a Tenure-track Associate Professor at Shanghai Jiao Tong University. Prior to that, he held postdoctoral researcher positions at the University of Oxford (United Kingdom) and at the Max Planck Institute for Nuclear Physics in Heidelberg (Germany), and earned his Ph.D. degree from Paris 7 University (France). He is interested in a number of topics in theoretical high-energy astrophysics and particle astrophysics, including cosmic-ray propagation, particle acceleration in pulsar wind nebulae, supernovae and supernova remnants, as well as gamma-ray astronomy. He is also interested in related plasma astrophysics problems, such as shock physics in the context of supernova shock breakout. He is the science working group coordinator of the Southern Wide field-of-view Gamma-ray Observatory (SWGO), and a member of the LHAASO Collaboration.Gamma-ray observations provide important information on cosmic-ray (CR) propagation in our Galaxy.First, we discuss TeV halos. We show that current gamma-ray measurements place interesting constraints on the turbulent magnetic fields around these pulsars, and we examine the implications for CR transport. Also, we suggest that extended gamma-ray sources of a hadronic origin should exist in the data. We show that such a source might exist in the AS-gamma data at 398-1000 TeV. Observations of this new type of sources could be used to constrain the Galactic magnetic field geometry.Second, we present a new model of anisotropic CR propagation in the Milky Way, where CRs are injected at discrete transient sources in the disc and propagated in Galactic magnetic field models. We then calculate the corresponding diffuse Galactic gamma-ray emission. We find that the expected diffuse gamma-ray emission at >~ 100 TeV is very clumpy, and does not correlate with the gas density along the line of sight. It is substantially different from the relatively smoother emission detected by Fermi at ~ GeV energies. We also discuss how many (hadronic) PeVatrons would be detectable in our simulations, and compare our predictions with LHAASO data. We show that this allows to place interesting constraints on CR transport in the Galaxy.Finally, we discuss the implications of the small-scale anisotropies observed in the TeV CR anisotropy, on CR propagation in the ISM.