Rustem

Good day, I'm student and i would like to ask a question about how molecule can go to the ground state from excited state, by absorbing the photons, in the end red shifted photons with lower energy are released. This is the principle of STED microscopy, that is used to limit amount of observed material. But me and teacher can not explain this situation. We were tough that if molecule absorbs photons/energy then it gets excited, but this situation is vice versa. I would be glad for any responses and answers, thanks!