This study has observed microscopic level cavitation processes in shelled second generation ultrasound contrast agent microbubbles. The spatial and temporal resolutions required for this undertaking have been achieved via a unique hybridisation of optical trapping with ultra high speed microphotography. Upon insonation with ultrasound in the region of 0.5-4MPa, microjets were observed to develop within, and subsequently issue from, cavitating bubbles. Jet impact into target substrates, including monolayers of biological cells, was observed. These observations provide direct evidence for the involvement of microjetting events during ultrasound exposure on live cells, a process that may have future potential as a novel non-invasive route to drug- and gene-based therapies.