Composite histological image of a LS174T xenograft combining information from hematoxylin and eosin, CA9, and CD31 stains depicts the complexity of the tumor, showing blood lakes (red), small necrotic regions (blue), widespread hypoxic regions (yellow), and red blood cells (white). The composition of the tumor matches the perfusion and oxygen saturation patterns seen in dynamic contrast–enhanced ultrasound (DCEUS) and photoacoustic (PA) imaging scans, respectively. When used in combination, DCEUS and PA imaging have the potential to facilitate the discrimination between blood lakes and necrotic areas. For details, see article by Bar-Zion and colleagues on page 4320.