The presence of cold blood, whether through acute seasonal chill or chronic environmental exposure, imposes an additional burden on the hearts’ ability to pump viscous blood around the body, potentially limiting blood flow to working muscle. Of particular interest is how the ‘business end’ of the cardiovascular system, the microcirculation, adapts under these conditions. Here, intimate contact between blood and tissue is achieved by a vast network of tiny vessels (capillaries) that facilitate supply of oxygen and other fuels, as well as removal of waste products. This lecture will explore some strategies that warm-blooded animals use to cope during winter, and contrast this with adaptations seen in cold-blooded animals that thrive in the constantly frigid waters around Antarctica. Stuart Egginton is a cardiovascular and muscle physiologist at the University of Leeds, where he is Professor of Exercise Science. His work explores biological limits to activity, and how flexibility is essential to cope with physiological challenges. He is a Fellow of The Physiological Society, currently a Monitoring Editor for the Journal of Experimental Biology, and has served as President of the British Microcirculation Society.