Research at the Department of Astronomy and Theoretical Physics concerns the structure of matter from the smallest to the largest scales. The department has three sub-units: Theoretical Particle Physics, Computational Biology & Biological Physics and Lund Observatory. At Theoretical Particle Physics we study the smallest constituents of matter and how these interact with each other. We work on phenomenology, from computer simulations of particles colliding at high energy to physics beyond the Standard Model. In Computational Biology & Biological Physics we build models of macromolecules and living systems and investigate biological processes by applying machine learning and statistical techniques. Research at Lund Observatory has as a common focus the formation and evolution of the Milky Way and its constituents. We study observationally and theoretically stellar populations, exoplanets as well as black holes, supernovae, and gamma-ray bursts.