‘The data explosion’ introduces the reader to the diversity of data in general before explaining how the digital age has led to changes in the way we define data. Big data is introduced informally through the idea of the data explosion, involving computer science, statistics, and the interface between them. It discusses search engine data, healthcare data, astronomical data, and real-time data such as the information provided by Global Positioning Systems. But what use is all this data? The ultimate aim of working with big data is to extract useful information. Combining traditional statistics and computer science allows large datasets to be analysed to search for key patterns.