A. Michel Peyrard^* and Yannick Sire^**

^*Laboratoire de Physique, Ecole Normale Sup΄erieure de Lyon 46 all΄ee d Italie, 69364 Lyon Cedex 07, France

^** Laboratoire Math΄ematiques pour l Industrie et la Physique, INSA, d΄ep. GMM, 135 avenue de Rangueil, 31077 Toulouse Cedex 4, France

This report, initially prepared to introduce a discussion on breathers in biomolecules, discusses some experimental results and their connection with theory. Classical vibrations are considered first and quantum effects are discussed in a second part. The paper does not intend to be a complete review of nonlinear localisation in molecules, but instead it introduces and discusses a few examples with the aim of stimulating thoughts and hopefully further experimental studies or theoretical investigations paying particular attention to the experimental aspects.