GFP imaging can reveal details of ductal development, mammary tumors, tumor associated blood vessels, and lymph node morphology. Ductal development can be compared with two imaging techniques – by first GFP imaging the mammary gland (A, C) and then whole mounting the same gland (B, D). Mammary tumors appear less bright compared to the mammary ducts (E) and more bright compared to tumor associated blood vessels (F-H). Lymph nodes (I) can be highlighted close to brighter mammary ducts (K). (J) H&E section of a lymph node. Arrows: mammary ducts, ^: mammary tumor, open arrowheads: blood vessels, *: lymph node. Magnifications are as indicated.