Autodidacticism (also autodidactism) is a contemplative, absorbing process, of "learning on your own" or "by yourself", or as a self-teacher. Some autodidacts spend a great deal of time reviewing the resources of libraries and educational websites. One may become an autodidact at nearly any point in one's life. While some may have been informed in a conventional manner in a particular field, they may choose to inform themselves in other, often unrelated areas. Notable autodidacts include Abraham Lincoln (U.S. president), Srinivasa Ramanujan (mathematician), Michael Faraday (chemist and physicist), Charles Darwin (naturalist), Thomas Alva Edison (inventor), Tadao Ando (architect), George Bernard Shaw (playwright), Frank Zappa (composer, recording engineer, film director), and Leonardo da Vinci (engineer, scientist, mathematician).