Tolkien created a legendarium, a fictional mythology about the remote past of Earth, of which Middle-earth in particular is the main stage. Parts of his legendarium are The Hobbit and The Lord of the Rings. The Silmarillion and The History of Middle-earth series (published by his son, Christopher Tolkien, posthumously) revealed Tolkien’s lifelong work on that same legendarium, a process which he called “sub-creation”. Tolkien’s other published works includes philological essays, modern adaptations of medieval literature and rendering of stories originally told to his children but not directly related to the legendarium.