  Clusters in the three-dimensional Ising model rigorously obey reducibility
and thermal scaling up to the critical temperature. The barriers extracted from
Arrhenius plots depend on the cluster size as $B \propto A^{\sigma}$ where
$\sigma$ is a critical exponent relating the cluster size to the cluster
surface. All the Arrhenius plots collapse into a single Fisher-like scaling
function indicating liquid-vapor-like phase coexistence and the univariant
equilibrium between percolating clusters and finite clusters. The compelling
similarity with nuclear multifragmentation is discussed.
