Laser-irradiated microclusters can generate energetic ions that produce fusion reactions. The amount and spectrum of these ions depend on the cluster-size distribution, electron heating mechanism, and cluster expansion dynamics. This paper describes recent physics results pertinent to the items listed. It is shown that the size distribution of large clusters can be determined from absorption measurements in a pump-probe experiment. It is also shown how a laser can create a two-component electron distribution with a hot minority whose energies exceed the ponderomotive potential. The heating rate and the limitations on electron energy are examined. The hot electron component expands with an equal number of ions. A first-principle model is presented that describes ion acceleration by the hot electron pressure together with adiabatic cooling of the hot electrons.