  We investigate monopoles in four-dimensional compact U(1) with Wilson action.
We focus our attention on monopole clusters as they can be identified
unambiguously contrary to monopole loops. We locate the clusters and determine
their properties near the U(1) phase transition. The Coulomb phase is
characterized by several small clusters, whereas in the confined phase the
small clusters coalesce to one large cluster filling up the whole system. We
find that clusters winding around the periodic lattice are absent within both
phases and during the transition. However, within the confined phase, we
observe periodically closed monopole loops if cooling is applied.
