Single‐cell sequencing (SCS) technology has revolutionized the study of cellular heterogeneity by enabling the exploration of biological processes at high resolution. While traditionally applied to mammalian models, recent advancements have extended SCS to ecologically and evolutionarily crucial lower vertebrates (particularly fish) and diverse invertebrates (including Urochordata, Echinodermata, Arthropoda, Mollusca, and Coel...