INER-37 and INER-51 MTS morphology. Left panels correspond to INER-37 spheroids while right panels are INER-51 spheroids. Panels A and B show an ultramicrographic photograph of the respective MTS after 72 hours of in vitro culture (200X). Panels C to F are different H&E staining microphotographs of the MTS. For panels C and D, the amplification was 400X, and for E and F it was 1200X.