  In this paper, we investigate some properties on harmonic functions and
solutions to Poisson equations. First, we will discuss the Lipschitz type
spaces on harmonic functions. Secondly, we establish the Schwarz-Pick lemma for
harmonic functions in the unit ball $\IB^n$ of $\IR^n$, and then we apply it to
obtain a Bloch theorem for harmonic functions in Hardy spaces. At last, we use
a normal family argument to extend the Landau-Bloch type theorem to functions
which are solutions to Poisson equations.
