Optogenetics, which uses light-sensitive proteins to regulate cellular activity, has transformed developmental biology by allowing precise spatiotemporal control of the critical signaling pathways. When paired with organoid technology, optogenetics offers an extraordinary tool for investigating differentiation, tissue morphogenesis, and organogenesis. This review examines the recent progress in the optogenetic manipulation of organoids, emphasizing its applications in directing stem cell differentiation, analyzing tissue morphogenesis, and modeling organ development. In neural differentiation, optogenetics has been used to activate Wnt signaling, fostering the generation of neural progenitors. Similarly, in cardiac differentiation, light-induced modulation of the BMP and Wnt pathways has supported the formation of functional cardiomyocytes. Optogenetic tools also enable researchers to explore the mechanical forces in tissue development by regulating cytoskeletal factors such as RhoA and Rac1. Furthermore, researchers can investigate organ patterning and regeneration by activating specific morphogens, such as Sonic hedgehog or Notch. Despite these advancements, challenges persist, such as enhancing light delivery in three-dimensional structures and developing more precise genetic engineering techniques. Future directions should involve integrating optogenetics with high-throughput imaging and single-cell analysis to improve the understanding of tissue development and disease modeling.This review underscores optogenetics as a groundbreaking approach for propelling stem cell research, regenerative medicine, and developmental biology.

Objectives: . The relationship of estrogen (the primary female sex hormone) with hearing function has been studied in both humans and animals. However, whether estrogen levels affect hearing remains uncertain. Therefore, in this study, we investigated changes in the vulnerability of hearing to acoustic overexposure in ovariectomized female rats. Methods: . Eighteen 8-week-old female Sprague-Dawley rats were separated into four groups as follows: sham ovariectomy (OP), OP only, and OP treated with low (10 µg/kg) or high doses (100 µg/kg) of estrogen. Rats in the estrogen replacement groups were given two intraperitoneal injections. Hearing thresholds were measured before noise exposure, and at 1 day and 2 weeks after exposure. Results: . The hearing thresholds of the sham OP and OP-only groups were not significantly different. However, both estrogen groups showed a lower threshold shift than the OP-only group. Histological immunostaining analyses showed that hair cell loss in the 32 kHz region was more severe in the sham OP group than in the OP-only group. Furthermore, there was little or no hair cell loss in either estrogen replacement group and significantly more hair cell loss in the OP-only group. Conclusion . These results suggest that estrogen replacement may reduce the vulnerability of hearing to noise exposure in menopausal women.