As W. Edward Deming said, “In God we trust, others must bring data”. In the last decades, the importance of data has increased consistently in many application fields, e.g. medicine, marketing, computer science and so on. However, raw data need to be processed in order to exploit useful information. In particular, the dynamic visualization of data is a key element in the data manipulation workflow. Inspired by the previous consideratons, this talk focuses on data-driven approaches that, linking data with SVG and DOM elements, help you design clear and interactive data visualizations. At the Umbrian Cancer Registry (R.T.U.P.), working side by side with physicians, we used d3.js to provide several statistics about the cancer incidence and mortality including temporal trends, age distributions and geographical distributions (http://www.rtup.unipg.it/SGrtup/Statistiche). Starting from the R.T.U.P. case of study, we show the basis and the underlying concepts of d3.js library. Methods to perform efficient document manipulation based on data are presented, applying data-driven transformations to the DOM in order to pair each element in the data array with the corresponding DOM node. The main elements of d3.js library, including selections, scales, axis and d3 layouts, are described providing specific examples.