The production, observation and manipulation of very small objects is a tour
de force, but these objects, which could infiltrate anywhere without being
seen, may arouse suspicion. To assess the situation at best, we describe the
activity of a nanoscience research institution, some of the methods used there,
the spirit of its researchers and their attitude towards risk.Comment: article accept\'e pour publication dans les C.R. Physique. El\'ement
d'un dossier 'Nanosciences et nanotechnologies: esp\'erances et
inqui\'etudes". D'autres articles de ce dossier, ainsi que la version
fran\c{c}aise de cet articles, seront \'egalement soumis \`a HA
