A solution (e.g., methylene blue, amylase-degraded microspheres) intended to be used as an in vivo tissue- or fluid-staining visualization aid during and/or after open or minimally-invasive surgery, particularly for delineation of tissues and operative pieces, seal testing sutures, and/or detection of leaks (e.g., pancreatic juice) and fistulas. Exact usage depends on the requirements of the surgeon and the surgical procedure performed. It is typically supplied in a glass vial or syringe. After application, this device cannot be reused.