The development of mosquito transgenesis technologies was driven by the need to make stable and heritable modifications to the genomes of these important insects for a variety of basic and applied objectives. While a number of transient assay systems for gene expression analyses were developed, transposable elements (TEs) were the first tools that allowed the production of genetically manipulated strains for studies that involve the complex biology of these insects and their ability to transmit pathogens. TEs have been replaced more recently for most applications by the adaptation of Cas9/guide RNA techniques, but they are still useful in randomly sampling genomes as enhancer traps and identifying neutral regions in the genome free of insertion site effects. Coupled with the Cas9/guide RNA technologies, precise editing and engineering of the genetic mechanisms responsible for much of the biology of these interesting and important insects is now possible.