The conference is the 15th in a series that was previously held under the name ‘Hole Burning, Single Molecule, and Related Spectroscopies (HBSM)’. The conference topics include, for example, single molecules and quantum dots, single ions and defect centers in solids, perovskite nanophysics, molecular quantum photonics and biophotonics, nanooptics and plasmonics, energetics and dynamics of biomolecules, etc.