About 180 inventions are described in chronological order, with an emphasis on how the invention developed, what problem they were designed to solve and their significance to contemporaries - and to subsequent events. Headings give the name and date of the invention and inventor. Subjects include writing, the watch, the rifle, the vacuum cleaner, the electronic computer and the contraceptive pill. Everything is grouped under various sections from the ancient world, the enlightened world and the modern world amongst others.