If you want to understand the realities of everyday life in 17th century London, there is no better starting point than Samuel Pepys’ diary. Researchers and designers know the power of diary studies, which is why they are a valuable tool to allow people to to conveniently express the events and details of their personal lives.This approach is a great way to accurately record behaviours and the rich context of those behaviours over time, allowing them to record feelings, thoughts and activities through the day, across the week or even over longer timeframes. Diaries are designed with instructions, examples and prompts to ensure that the most relevant information is recorded, and to make them convenient and portable to maximise the chances of compliance. For example, a diary may prompt participants for details whenever they engage in specific behaviours, use particular products or services or engage in relevant activities. Alternatively, prompts may be triggered at regular times of day or week to record a summary of a fixed period.