We have been using cell addresses informally until now, but now we can be more formal and explicit. Different spreadsheets have different types of address bars, but all use the same format, letters for columns and numbers for rows with letters first and numbers second. We introduce this on the hundreds table which could be thought of as a miniature spreadsheet and use number lines to provide some additional feedback. Using addressing enables us to build rules as patterns and to put anything we want into cells to use those rules on. It is the great power of spreadsheets.