What's the difference between a microsphere and a microcapsule?

A microsphere in a solid matrix particle whereas a microcapsule has an inner core and an outer shell.  The active ingredient in a solid matrix particle is typically dissolved or melted in the same vessel as the active ingredient before Precision Particle Fabrication processing into microspheres.  The microcapsule core can be either liquid (oil or water) or solid and typically contains the active ingredient.  The shell of a microcapsule is typically a polymer or wax.  Precision control of shell thickness and density can be used to achieve the desired release kinetics of the core.