  In contrast to the situation with the geodynamo, no breakthrough has been
made in the solar dynamo problem for decades. Since the appearance of
mean-field electrodynamics in the 1960's, the only really significant advance
was in the field of flux tube theory and flux emergence calculations. These new
results, together with helioseismic evidence, have led to the realization that
the toroidal magnetic flux giving rise to activity phenomena must be stored and
presumably generated below the convection zone proper, in what I will call the
DOT (Dynamo-Overshoot-Tachoclyne) layer. The only segment of the problem we can
claim to basically understand is the transport of flux from this layer to the
surface. On the other hand, as reliable models for the DOT layer do not exist
we are clueless concerning the precise mechanisms responsible for
toroidal/poloidal flux conversion and for characteristic migration patterns
(extended butterfly diagram) and periodicities. Even the most basic result of
mean-field theory, the interpretation of the butterfly diagram as an
alpha-omega dynamo wave, has been questioned. This review therefore will
necessarily ask more questions than give answers. Some of these key questions
are
  - Structure of the DOT layer
  - alpha-quenching and distributed dynamo
  - High-latitude migration patterns and their interpretation
  - The ultimate fate of emerged flux
