  We give a brief overview of the kinetic theory for spin-1/2 fermions in
Wigner function formulism. The chiral and spin kinetic equations can be derived
from equations for Wigner functions. A general Wigner function has 16
components which satisfy 32 coupled equations. For massless fermions, the
number of independent equations can be significantly reduced due to the
decoupling of left-handed and right-handed particles. It can be proved that out
of many components of Wigner functions and their coupled equations, only one
kinetic equation for the distribution function is independent. This is called
the disentanglement theorem for Wigner functions of chiral fermions. For
massive fermions, it turns out that one particle distribution function and
three spin distribution functions are independent and satisfy four kinetic
equations. Various chiral and spin effects such as chiral magnetic and votical
effects, the chiral seperation effect, spin polarization effects can be
consistently described in the formalism.
