Explain the process of animals genetically modified using DNA microinjection?

DNA microinjection is a process that is used, and has been used since 1980, to produce genetically modified organisms. It is most commonly used with mammalian DNA. Specifically, the technology is more often than not tested on and used with mice. Furthermore, DNA microinjection typically introduces DNA sequences that are not present in that particular species. This means that DNA microinjection technology is used to create transgenic organisms. Finally, the success rate of the process is incredibly low. It is reported as being successful only 10 percent to 20 percent of the time. This is because the DNA incorporation is random and might not happen, or it might interfere with critical DNA sequences that the organism needs to live in the first place.
The process of DNA microinjection is fairly straightforward and relatively low tech. A very fine pipette is used to "manually inject" DNA from one organism into the fertilized egg of another organism. The hoped for result is that the injected DNA will be incorporated/integrated into one of the chromosomes of the fertilized egg. Mitotic divisions will occur, and the new DNA sequences within that chromosome will be replicated. The fertilized egg is then transferred into the oviduct of a female. The organism is now pregnant and will hopefully give a normal birth to an organism that hopefully displays the transgene trait.
https://research.uci.edu/facilities-services/tmf/services/dna-micro.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3459342/

https://www.thebalance.com/microinjection-375568