Here, we report some examples from the developmental phases of successful and failed tissue engineering products, i.e., Holoclar® [1] and tracheal reconstruction [5], and two successful examples of gene therapy, i.e., a registered product (Strimvelis®) [3•] for the treatment of ADA deficiency and a phase I/II trial for the treatment of junctional epidermolysis bullosa [6]. This evidence concerns the gene ADA and Junctional epidermolysis bullosa, Herlitz type.