All-trans beta-carotene molecules have been deposited at room temperature on Cu (111) and subsequently studied by STM at liquid nitrogen. They form a self-organized multilayer structure. The STM images allow to unambiguously identify single molecules and to resolve important aspects of their internal structure like its curved backbone polyene chain, its attached methyl groups and the beta-ionone rings. We suggest that the molecules lose their center of symmetry, the molecule being flexible enough to allow the formation of large three-dimensional periodic extensions. (C) 2003 Elsevier Science B.V. All rights reserved.