Around 10% of us will experience kidney stones at some point in our life. They occur when waste products in the blood form small crystals, which gather together in the kidneys to form hard lumps. Small kidney stones (4mm in diameter) usually pass through the body naturally, with no medical intervention required. However, larger kidney stones may require treatment. For example, a laser beam can be used within the kidney to break a large stone up into smaller pieces. During this laser treatment, bubbles are formed in the kidneys - which can be a help or a hindrance. In this episode, we chat to applied mathematician Sophie Abrahams, who uses mathematical modelling to explore the best ways to pulse a laser to achieve the 'best bubbles' during the treatment of kidney stones.