Effects in the Hydrogen Atom Confined by Dihedral Angles -- Symmetry reduction and energy levels splitting of the one-electron atom in an impenetrable cavity -- The Confined Hydrogen Atom Revisited -- Quantum Confinement studies on two electron systems -- Study of Confined Quantum Systems using Variational Methods: A Review -- Photoionization and resonances in confined atoms -- Spatial and shell confinement of one electron atomic and molecular systems: structure and electric dipole polarizability -- Study of Quantum Confinement of H+2 ion with Monte Carlo Approach. Respective Role of the Electron and Nuclei Confinement -- Variational study of one and two-electron diatomic molecules confined by hard and soft prolate spheroidal cavities -- DFT chemical predictors for confined atoms.