What is an opportunistic infection? How are drugs trialled? What is "pharming'? The 'Why Science Matters' series demonstrates how the science we learn at school is important in every aspect of our everyday lives. Using case studies and investigations, the series describes the development of science and technologies that can improve our lives - or lead to new scientific challenges and controversies. In 'Finding Better Medicines', we learn how the body fights illness and infection and sometimes needs the help of medicines to be cured. We find how some drugs we now take for granted such as aspirin and penicillin were developed, how pharmaceutical companies research and improve new drugs, and how advanced technologies such as genetic engineering can be used to create plants and animals that can be farmed for medicines.