The Protogenoi (Πρωτογενοι) are the First Born Deities of the Greek Kosmos. They are the building blocks of the universe, primordial Deities. I have written before about Them, in a post about genealogy of the Gods.
The Protogenoi we know of are: Aether (Αἰθήρ, 'Light'), Ananke (Ἀνάγκη, 'Fate' or 'Compulsion'), Khronos (Χρόνος, 'Time'), Erebos (Ἔρεβος, 'Darkness'), Eros (Ἔρως, 'Desire' or 'Love'), Gaea (Γαῖα, 'Earth'), Hemera (Ἡμέρα, 'Day'), Hydros (Ὑδρος, 'Primordial Waters'), Khaos (χάος, 'Chaos' or 'Air'), Nêsoi (Νησοι, 'Islands'), Nyx (Νύξ, 'Night'), Ôkeanos (Ωκεανος, 'Water'), Ourea (Oὔρεα, 'Mountains'), Phanes (Φάνης 'Procreation'), Pontos (Πόντος, 'Sea'), Phusis (φύσις, 'Nature'), Tartaros (Τάρταρος), Thalassa (Θάλασσα, 'Sea'), Thesis (Θεσις, 'Creation'), Uranos (Οὐρανός, 'Sky').
As might have become apparently from the, previously mentioned, earlier published post; any mythology from this era is incredibly mucky. There are a few sources we can track the beginning of the universe to; because that is where the Protogenoi were born in--or from; the beginning of the universe. They are the embodiments of the aspects of life They are named after. Zeus may be Lord of the Sky, but the sky itself is a primordial Deity, distant from humanity but ever-present.