Explore a comprehensive lecture on many-body perturbation theory and wavefunction methods from a physics perspective. Delve into applications of multiscale modelling, the Schrödinger equation, product wavefunctions, and potential energy surfaces in supramolecular and photoelectronic systems. Examine various methods and solutions, including scaling of energy, correlation energy, molecular perturbation theory, and convergence of perturbation theory. Investigate screening, density functional theory (DFT), and its applications to real systems. Learn about explicit nonlocal approaches and noninteracting susceptibility in this in-depth presentation by Alexandre Tkatchenko from the University of Luxembourg, delivered at IPAM's Advancing Quantum Mechanics with Mathematics and Statistics Tutorials.