Embodiments of the invention provide both a new type of building set which, while particularly attractive to girls, is suitable for use with a wide variety of themes and is fun for boys as well. A building set teaches engineering and biology concepts. The set comprises interlocking pieces that users can manipulate and use to build structures. In some embodiments, the elements use two different types of connector, one type requiring a specific orientation of the connected elements and a second type allowing the connection to be made in any orientation. In some embodiments, one connection type, preferably the fixed orientation connector, uses one or more springy element that spring out to interlock with a mating component, and the other type of connection uses a friction fit. In one embodiment, the toy components are suited for forming a tree with interlocking branches and leaf-disks. The elements appeal to girls through use of color and story line. Users can build play scapes that are coordinated through plot, and are interchangeable to inspire creativity. The current invention also employs inventive locking techniques and structural elements.