  It has been realized for a long time that knowing the eta and eta^prime wave
functions in terms of quark and gluon components probes our understanding of
non-perturbative QCD dynamics. Great effort has been given to this challenge --
yet no clear picture has emerged even with the most recent KLOE data. We point
out which measurements would be most helpful in arriving at a more definite
conclusion. A better knowledge of these wave functions will significantly help
to disentangle the weight of different decay subprocesses in semi-leptonic
decays of D+, Ds^+ and B+ mesons. The resulting insights will be instrumental
in treating even non-leptonic B transitions involving eta and eta^prime and
their CP asymmetries; thus they can sharpen the case for or against New Physics
intervening there.
