Currently, the vast majority of medicines are prescribed in the form of a pill or injection with the drug transported throughout the body via the blood stream. For many conditions this is very effective. However, for diseases that require very powerful drugs, such as cancer or stroke, it poses a significant problem – only a very tiny proportion of the drug is actually delivered to the target site. The rest is absorbed by healthy tissue, often leading to serious side effects. Professor Stride (University of Oxford) will describe how tiny gas bubbles, 100 times smaller than a human hair, can be used to address this challenge by enabling “on demand” delivery of a drug to a target site.