Model organisms are key components in almost all biological research. This bachelor thesis represents an overview of key methods for delivery of large DNA constructs into model cell lines in culture and/or model organisms such as mice. Here, I also present an overview of their role as main experimental models. Genetic engineering and genetic modifications of cell and organismal models enabled unraveling the intricate networks of cellular processes involving many gene interaction and interactions of their products. The acquired knowledge enables understanding cellular processes underlying complex diseases, metabolic pathways and molecular basis of procreation. Development of new technologies led to establishment of CRISPR/Cas9 method originating from bacteria as one of the earliest examples of acquired “immunity”. Adaption of this technology into a precise genome editing tool holds almost unlimited potential in genetic engineering. Furtheromore, CRISPR/Cas9 system in combination with lentiviral technology for delivery of transgenes into in vitro (cells) and in vivo (organisms) models opens new avenues for development of gene therapy. The most useful viral models for delivery of trangenes are those from the family Retroviridae with the emphasis on the main model, the human immunodeficiency virus (HIV). Lentiviral gene delivery is especially important due to its ability to stably integrate the transgene of interest into the host genome for constitutive gene expression. Therefore, CRISPR/Cas9 system combined lentiviral delivery of transgenes represents state of the art methodology in gene therapy, but also in many other studies in molecular biology, biomedicine and medicine field.