In this clip from the 2008 Royal Institution Christmas Lectures we are introduced to Tara, who was born profoundly deaf, and who at the age of 3 received a cochlear implant which has given her the ability to hear. After looking at the digital technology of cochlear implants and how they work, we meet Tara herself, now aged 13, and also Roger Gray, the surgeon who carried out this remarkable operation. You can watch the 2008 Royal Institution Christmas Lectures in full at: http://research.microsoft.com/~cmbishop or by visiting the Royal Institution web site. There is a dedicated web site to accompany the 2008 Christmas Lectures, with ten interactive games as well as downloadable PDF instructions for experiments which can be conducted at home or at school: http://www.rigb.org/christmaslectures08