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Known for being highly sensitive and noninvasive, ultrasound imaging using microbubble contrast agents is widely used in the clinic. To use ultrasound to image tissue beyond the vasculature, researchers have developed strategies that include nanobubbles, ultrasound contrast agents generated in situ, and gene expression of ultrasound contrast agents in situ. All of these strategies offer the capability of targeting tumor cells, intratumoral imaging tumor cells and require just a small incision or no incision. In this review, we will first describe the application of nanobubbles acting as ultrasound contrast agents. Then, we will briefly introduce the stimuli-responsive formulations to generate ultrasound contrast agents in situ. Finally, we will provide an overview of the use of state-of-the-art of gene expression of ultrasound contrast agents in situ to monitor cellular location and function inside living organisms.