We hereby attach an essay published by Nature 456, 444-445 (27 November 2008) | doi:10.1038/456444a; Published online 26 November 2008. Elena Cattaneo is a professor in the Department of Pharmacological Sciences, director of the Centre for Stem Cell Research, University of Milan, Italy and member of the Promoting Committee of the World Congress for Freedom of Scientific Research. Prof. Cattaneo has asked Nature to donate her honorarium for this essay to Luca Coscioni Association, namely for the organization of the next meeting of the World Congress.