The increasing number of patients with chronic diseases implies the necessity of developing drugs for a longer period and taking a lot of medicines simultaneously, which may lead to a decrease in patient compliance. This problem is serious for drugs with short biological half lives because they must be taken more frequently. A solution might be the development of a dosage form capable of releasing the drug gradually. In this regard, microencapsulation has been used as one of the methods to construct a formulation for delivering the drug in a controlled mode. This book provides chemistry of salbutamol sulphate, tramadol hydrochloride, diclofenac sodium and ethylcellulose, physics of drug release through particle wall and use of microparticles in life sciences. Microparticles were prepared by using three different microencapsulation techniques i.e. coacervation thermal change, solvent evaporation and coacervation non-solvent addition by adjusting the ratio of drug to ethylcellulose (release retardant material). This presentation narrates a complete guideline from formulation development by microencapsulation to the conductance of biowaiver study.