The spontaneous formation of density waves has been fascinating me since Harald Puhl and myself saw them first in a totally amateurish experiment in HLRZ. Then came Thorsten Poeschel and brought some more professional glass pipes and finally Tareck Raafat made a PhD thesis under the joint guidance with Jean Pierre Hulin. This experiment gave rise to a first paper published in Phys. Rev. E, Vol.53, p.4345-4350 (1996).