Triggering knowledge panels

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for providing knowledge panels with search results. In one aspect, a method includes receiving a query. Search results that are responsive to the query are obtained. A first set of factual entities referenced by the query are identified. A particular factual entity is selected from the first set. It is determined that a knowledge panel for the particular factual entity is to be provided with the search results based, at least in part, on content of the knowledge panel and characteristics of the search results. The knowledge panel can include at least one content item, for the selected factual entity, received from a first resource and at least one content item, for the selected factual entity, received from a second resource different than the first resource. The knowledge panel is provided.