  We discuss the geometry of homogeneous Ricci solitons. After showing the
nonexistence of compact homogeneous and noncompact steady homogeneous solitons,
we concentrate on the study of left invariant Ricci solitons. We show that, in
the unimodular case, the Ricci soliton equation does not admit solutions in the
set of left invariant vector fields. We prove that a left invariant soliton of
gradient type must be a Riemannian product with a nontrivial Euclidean de Rham
factor. As an application of our results we prove that any generalized metric
Heisenberg Lie group is a nongradient left invariant Ricci soliton of expanding
type.
