  We study the 3D topology of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM)
single-modes, which includes bubbles, jets and saddle points. We present an
analytic description of the interface as a whole, for arbitrary time-dependant
acceleration g(t). The dependance of morphology on the lattice - Hexagonal,
square or triangular -of bubbles are investigated. RM accelerations in the case
of a large density ratio produce jets well separated from each other while, in
RT case, jets are connected by liquid sheets. We compare our analytic results
to numerical simulations.
