Gene Delivery: Methods and Applications provides a comprehensive overview on viral and non-viral methods used to genetically engineer human mesenchymal stromal cells. In addition, an update on ongoing and completed clinical studies with engineered mesenchymal stromal cells will be provided, as well as a snapshot of the advances and technical challenges yet to be addressed. Next, a variety of gene delivery systems including physical transfection techniques, virus-based delivery vectors, chemically engineered delivery systems and bio-inspired vehicles are reviewed and their strengths, shortcomings and biomedical applications are discussed. Selfish DNA called transposons capable of cutting out and pasting into the host genome are active throughout the phylogenetic kingdoms. Researchers have repurposed natural transposons for use in delivering a gene-of-interest, enabling for the study of a large and growing list of preclinical gene therapy applications. As such, the authors discuss the past achievements and future challenges of this early-stage technology. The closing chapter introduces cell-penetrating peptides as an efficient tool for DNA transfection. HR9, a designed cell-penetrating peptides, containing nona-arginine flanked by cysteine and penta-histidine displayed a high penetrating ability in mammalian cells.