By the mid-19th century many of the new national museums of Europe were in place, and holding exhibitions of their own collections, or loaned collections, or a mixture of objects from both sourcers, which remains a typical mix today. The "Chronology of Temporary Exhibitions at the British Museum" goes back to 1838. The tradition of the Universal exposition "world Expo" or "World's Fair" began with the Great Exhibition of 1851 in London; these are only held every few years. The Eiffel Tower in Paris was built for the Exposition Universelle (1889) and served as an entrance arch. Modern exhibitions may be concerned with preservation, education and demonstration, early exhibitions were designed to attract public interest and curiosity. Before the widespread adoption of photography, the exhibition of a single object could attract large crowds. Visitors might even be overcome with Stendhal syndrome, feeling dizzy or overwhelmed by the intense sensory experience of an exhibit. Today, there is still tension between the design of exhibits for educational purposes or for the purpose of attracting and entertaining an audience, as a tourist attraction. Art exhibitions include an array of artifacts from countless forms of human making: paintings, drawings, crafts, sculpture, video installations, sound installations, performances, interactive art. Art exhibitions may focus on one artist, one group, one genre, one theme or one collection; or may be organized by curators, selected by juries, or show any artwork submitted. Fine arts exhibitions typically highlight works of art with generous space and lighting, supplying information through labels or audioguides designed to be unobtrusive to the art itself. Exhibitions may occur in series or periodically, as in the case with Biennales, triennials and quadrennials. The first art exhibition to be called a blockbuster was allegedly the 1960 Picasso show at Tate in London. Interpretive exhibitions are exhibitions that require more context to explain the items being displayed. This is generally true of exhibitions devoted to scientific and historical themes, where text, dioramas, charts, maps and interactive displays may provide necessary explanation of background and concepts. Interpretive exhibitions generally require more text and more graphics than fine art exhibitions do. The topics of interpretive graphics cover a wide range including archaeology, anthropology, ethnology, history, science, technology and natural history. Commercial exhibitions, generally called trade fairs, trade shows or expos, are usually organized so that organizations in a specific interest or industry can showcase and demonstrate their latest products, service, study activities of rivals and examine recent trends and opportunities.