Ever since the discovery that one or more compounds in the thyroid could accelerate anuran metamorphosis over a century ago (Gudernatsch, 1912), anuran metamorphosis has been used as a model for studying postembryonic development in vertebrates, particularly the role of thyroid hormone (T3) during metamorphosis, and developmental regulation of organ regeneration (Dodd & Dodd, 1976; Gilbert & Frieden, 1981; Gilbert, Tata, & Atkinson, 1996; Li, Zhang, & Amaya, 2016; Marshall et al., 2019; Shi, 1999, Shi, 2013a; Tata, 1993; Wang & Shi, 2021; Yakushiji, Yokoyama, & Tamura, 2009). Metamorphosis in anurans, such as the highly related diploid Xenopus tropicalis and pseudo-tetraploid Xenopus laevis, resembles postembryonic development in mammals, a period around birth when plasma T3 level peaks and many organs/tissues mature into their adult form (Fig. 1A) (Shi, 1999; Tata, 1993). While it is difficult to study mammalian postembryonic development due to maternal influence, it is much easier to manipulate anuran metamorphosis. T3 plays a causative role in this process and its level can be easily altered by adding exogenous T3 or T3 synthesis inhibitors to tadpole rearing water to affect metamorphosis. In addition, T3 can even induce organ-specific metamorphic changes when added to organ cultures of premetamorphic tadpoles, indicating that individual tissues/organs are genetically programmed for specific T3-dependent changes. Furthermore, essentially all tissues/organs in an anuran tadpole are transformed during metamorphosis, involving drastic changes ranging from de novo formation of adult tissues such as the limb, remodeling of organs present in both tadpoles and frogs to adapt for post-metamorphic living habitat, to complete resorption of larval specific organs such as the tail (Fig. 1B). This makes it possible to use anuran metamorphosis to study diverse cellular processes during vertebrate development. The advantage of the anuran model is further strengthened by transgenic and gene-editing tools for genetic studies (Blitz, Biesinger, Xie, & Cho, 2013; Fu, Buchholz, & Shi, 2002; Kroll & Amaya, 1996; Lei et al., 2012; Lei, Guo, Deng, Chen, & Zhao, 2013; Nakade et al., 2014; Nakayama et al., 2013; Shi et al., 2015; Wang et al., 2015; Young et al., 2011), which had been a weakness for amphibian and fish models compared to the mouse model for vertebrate studies.