Amphibians like X. laevis are suitable for experimental embryology because they have large embryos that can be easily manipulated and observed during development. In experiments with axolotls, mutants with white pigmented skin are often used because their semi-transparent skin provides an efficient visualization and tracking method for fluorescently tagged proteins like GFP. Amphibians are not always ideal when it comes to the resources required to produce genetically modified animals; along with the one to two-year generation time, Xenopus laevis can be considered less than ideal for transgenic experiments because of its pseudotetraploid genome. Due to the same genes appearing in the genome multiple times, the chance of mutagenesis experiments working is lower. Current methods of freezing and thawing axolotl sperm render them nonfunctional, meaning transgenic lines must be maintained in a facility and this can get quite costly. Producing transgenic axolotls has many challenges due to their large genome size. Current methods of generating transgenic axolotls are limited to random integration of the transgene cassette into the genome, which can lead to uneven expression or silencing. Gene duplicates also complicate efforts to generate efficient gene knockouts. Despite the costs, axolotls have unique regenerative abilities and ultimately provide useful information in understanding tissue regeneration because they can regenerate their limbs, spinal cord, skin, heart, lungs, and other organs. Naturally occurring mutant axolotls like the white strain that are often used in research have a transcriptional mutation at the Edn3 gene locus. Unlike other model organisms, the first fluorescently labeled cells in axolotls were differentiated muscle cells instead of embryos. In these initial experiments in the early 2000s, scientists were able to visualize muscle cell regeneration in the axolotl tail using a microinjecting technique, but cells could not be traced for the entire course of regeneration due to too harsh conditions that caused early cell death in labeled cells. Though the process of producing transgenic axolotls was a challenge, scientists were able to label cells for longer durations using a plasmid transfection technique, which involves injecting DNA into cells using an electrical pulse in a process called electroporation. Transfecting axolotl cells is thought to be more difficult because of the composition of the extracellular matrix (ECM). This technique allows spinal cord cells to be labeled and is very important in studying limb regeneration in many other cells; it has been used to study the role of the immune system in regeneration. Using