@pentaxuser Here is my relatively non-technical explanation: Paper (and film) is coated with an emulsion of silver halides (chloride, bromide, iodide). For simplicity's sake let's say silver chloride. When that silver chloride is exposed to light some of it is converted to metallic silver from the energy contained in the light but it is a tiny amount and cannot be seen. This is the "latent image". When the film is placed in developer more of the silver chloride is turned into metallic silver which forms an image that is useful. The fixer removes the silver chloride that did not turn into metallic silver (the unexposed parts). If you were to take the film from the developer and put it in stop then no more development occurs but the silver chloride is still there and can form a new latent image in response to light so if you put it back in developer before fixing (and had exposed the film to light when it was in the stop bath) it would just fog completely. If you want to develop by inspection you have to use orthochromatic film that is insensitive to red safelight.
