the human IgE molecules in the cell walls of basophils (with their histamine granules) are challenged with an antibody (the antibody is a goats IgE [anti-human IgE]) and with iteratively diluted (and agitated) successive solutes: degranulation is scored/counted.

Degranulation was observed which, to begin with, diminishes with successive iterations/dilutions, but then returns (and disappears again) in a cyclical fashion.
Activity was seen at dilutions beyond Avagadro's number!

the original experiment in Benveniste's lab was replicated by three reputable laboratories in the 1980s, (see Davenas)

and a decade later a similar demonstration was performed by five laboratories (see the Guardian and/or Belon P et al Inhibition of human basophil degranulation by successive histamine dilutions: results of a European multi-centre trial. Inflamm Res. 1999 Apr;48 Suppl 1:S17-8.