In cardiology and radiology, ultrasound contrast agents (UCAs) are routinely used to assess blood perfusion using contrast-enhanced ultrasound imaging. An example of an UCA is microbubbles that have a core of gas which is stabilized by a shell consisting of a lipid, protein, sugar and/or polymer. These microbubbles have a diameter of ~1 to 10 µm. When exposed to ultrasound, the microbubble’s gas core responds to the pressure change by compressing and expanding, which results in the vibration of the microbubble. This vibration provides acoustic signals for contrast-enhanced ultrasound imaging and can stimulate and enhance cellular drug uptake. Although the initial use of UCA was for diagnostic imaging only, their potential as local drug delivery systems is nowadays well established and further expansion of their use is expected. In addition to this, clinical studies show the safety of the microbubble-mediated treatment. At the same time, a more detailed insight into the underlying mechanism of the microbubble-cell-drug interaction is needed for maximum therapeutic outcome and widespread clinical use. For contrast-enhanced ultrasound imaging, novel pulsing schemes or beamforming techniques continue to be developed for better diagnostics through for example enhanced resolution. This methods collection aims to collate models to investigate ultrasound contrast agents and cavitation nuclei for imaging and therapy, both in vitro and in vivo. These models will offer existing and new researchers in the ultrasound contrast agent and cavitation nuclei field a resource providing in-depth details as well as advantages and limitations of each current model.