Atum, the uncreated creator, emerges from the waters on his mound in the form of Khepri the dung beetle. Khepri represents the sun at morning, and his name means "He Who Becomes" (or something like that). He later takes the form of Ra, the sun at noon. Oddly enough, the setting sun is seen as Atum in the form of an old man with a staff. I think this has to do with the belief that Atum will one day dissolve the universe and return to the waters of Nun. It's said that Osiris will join him, being the only thing besides Atum that will continue to exist.
Atum, being alone, creates Shu and Tefnut. I'll talk more about that next time. He does this through heka (magic). Heka, personified as a god, boasts in inscriptions that he existed before all the gods. Some view the Memphite version as being the first full expression of what would later become logos philosophy, but I think the Heliopolitan version does so just as well. Heka or Shu (depending on which version of the myth you use--in fact, the two are interchangeable) is the agency through which the gods and the world are created, which is logos philosophy.
Ta-tenen is an earth god who was associated with the primordial mound, and the mound was often called by his name. More commonly it was known as the benben. This was also the name of the capstone of obelisks and pyramids, which were representations of the primordial mound.