This volume presents detailed laboratory protocols for in vitro synthesis of mRNA with favorable properties, its introduction into cells by a variety of techniques, and the measurement of physiological and clinical consequences such as protein replacement and cancer immunotherapy. Synthetic techniques are described for structural features in mRNA that provide investigational tools such as fluorescence emission, click chemistry, photo-chemical crosslinking, and that produce mRNA with increased stability in the cell, increased translational efficiency, and reduced activation of the innate immune response. Protocols are described for clinical applications such as large-scale transfection of dendritic cells, production of GMP-grade mRNA, redirecting T cell specificity, and use of molecular