  In this paper, we consider the global wellposedness of 3-D incompressible
magneto-hydrodynamical system with small and smooth initial data. The main
difficulty of the proof lies in establishing the global in time $L^1$ estimate
for the velocity field due to the strong degeneracy and anisotropic spectral
properties of the linearized system. To achieve this and to avoid the
difficulty of propagating anisotropic regularity for the transport equation, we
first write our system \eqref{B1} in the Lagrangian formulation \eqref{B11}.
Then we employ anisotropic Littlewood-Paley analysis to establish the key $L^1$
in time estimates to the velocity and the gradient of the pressure in the
Lagrangian coordinate. With those estimates, we prove the global wellposedness
of \eqref{B11} with smooth and small initial data by using the energy method.
Toward this, we will have to use the algebraic structure of \eqref{B11} in a
rather crucial way. The global wellposedness of the original system \eqref{B1}
then follows by a suitable change of variables together with a continuous
argument. We should point out that compared with the linearized systems of 2-D
MHD equations in \cite{XLZMHD1} and that of the 3-D modified MHD equations in
\cite{LZ}, our linearized system \eqref{B19} here is much more degenerate,
moreover, the formulation of the initial data for \eqref{B11} is more subtle
than that in \cite{XLZMHD1}.
