  Given a set of collective variables, a method is proposed to obtain the
associated conjugated collective momenta and masses starting from a microscopic
time-dependent mean-field theory. The construction of pairs of conjugated
variables is the first step to bridge microscopic and macroscopic approaches.
The method is versatile and can be applied to study a large class of nuclear
processes. An illustration is given here with the fission of $^{258}$Fm. Using
the quadrupole moment and eventually higher-order multipole moments, the
associated collective masses are estimated along the microscopic mean-field
evolution. When more than one collective variable are considered, it is shown
that the off-diagonal matrix elements of the inertia play a crucial role. Using
the information on the quadrupole moment and associated momentum, the
collective evolution is studied. It is shown that dynamical effects beyond the
adiabatic limit are important. Nuclei formed after fission tend to stick
together for longer time leading to a dynamical scission point at larger
distance between nuclei compared to the one anticipated from the adiabatic
energy landscape. The effective nucleus-nucleus potential felt by the emitted
nuclei is finally extracted.
