A "developing tank" is a container used in photography for processing film. It allows photographers to develop their exposed film in a controlled environment, protecting it from light while the chemicals work. The tank typically includes a lid and a spool to hold the film in place during the development process. Inside the developing tank, various chemicals, such as developer, stop bath, and fixer, are used sequentially to create the final image. This process is essential for both black-and-white and color films, making the developing tank a crucial tool for anyone working with traditional film photography, including enthusiasts and professionals alike.