Continuous efforts are under progress in the eld of advanced drug-delivery research. Pharmaceutical scientists, along with bioengineers, biophysicists, and biomedical scientists, are actively being involved in the interdisciplinary research activities for the formulation and optimization of advanced drug-delivery system. A well-designed controlled drug-delivery system is always capable of delivering the agent to the target tissue in the optimal amount in the specied period of time there by causing little toxicity and minimal side effects with maximum therapeutic efcacy. Recently, many efforts are being made on the fabrication of polymeric microparticles, also sometimes termed as microcapsules or microspheres. A typical microsphere and microcapsule are given in Figure 14.1.