Conclusions
An overview of optical spectroscopy on trapped atoms has been presented. The subject is a hot topics in the atomic physics community and has also applications in other fields like nuclear physics. The advantages of a cold and dense atomic sample in performing spectroscopy have been shown together with possible applications. New properties of atoms at ultralow temperatures and new methods have been reported. The possibilities extend beyond pure atomic physics as photoassociative spectroscopy opens the way to the investigation of weakly bound molecules.