Plastics are one of the most useful substances known to man, strong, durable and abundant, but once in the environment, they are here to stay. Professor Andrea Sella tells us about the unique properties of carbon-based plastics - why they are so useful and why they are so hard to get rid of. And, Dr Susan Mossman, a materials science specialist at the Science Museum, gives us a plastics history lesson which has a few surprises along the way. But what happens when the high cost of hydro-carbons make plastics too expensive? Head of the National Non-Food Crops Centre in York, Dr Jeremy Tomkinson, is amongst those out there looking for alternatives. He tells us what a new generation of plastics might have to offer.