The sign of the times is usually linked to disapproving, something that is typical of the bad way things are now. On the other side, the sign of the times is marked by changes that indissolubly link past, present and future. Some call it progress. A history as long as humankind. From alchemists in search of the philosopher’s stone, to the discovery of the atom and DNA. From the study of birds, to the airplanes and interstellar flight. From the study of human anatomy, to artificial intelligence. From the classification of plants, to chemistry and medicine. Positive or negative? You choose, building the story of your favorite pictures with this collection that combines past and present in warm and vibrant colors.