  In the spin-Peierls compound CuGeO$_{3}$, the commensurate-incommensurate
transition concerning the modulation of atomic position and the local
spin-polarization is fully monitored at T=0 by the application of an external
magnetic field ($H$) above a threshold value $H_{c}\simeq $ 13 Tesla. The
solitonic profile of the spin-polarization, as well as its absolute magnitude,
has been precisely imaged from $^{65}Cu$ NMR lineshapes obtained for
$h=(H-H_{c})/H_{c}$ varying from 0.0015 to 2. This offers a unique possibility
to test quantitatively the various numerical and analytical methods developed
to solve a generic Hamiltonian in 1-D physics, namely strongly interacting
fermions in presence of electron-phonon coupling at arbitrary band filling.
