John 3:13

καὶ οὐδεὶς ἀναβέβηκεν εἰς τὸν οὐρανὸν εἰ μὴ ὁ ἐκ τοῦ οὐρανοῦ καταβάς, ὁ υἱὸς τοῦ ἀνθρώπου ὁ ὢν ἐν τῷ οὐρανῷ.

Rough Word-by-word:
And no one he has gone up into the heaven if not the out of the heaven having gone down, the son the of man the one being in the heaven.

Smooth Translation:
And no one has gone up into heaven if not having gone down from heaven, the son of man in heaven.

Notes:
What a heavenly verse. Jesus, being in heaven, came down out of heaven and went up into heaven. The divine incarnation is being clearly spoken about here.

καὶ conjunction "and"

οὐδεὶς adjective nominative masculine singular "no one"

ἀναβέβηκεν verb perfect active indicative 3rd singular from ἀναβαίνω (I go up) "he has gone up"

εἰς accusative preposition "into"

τὸν definite article accusative masculine singular "the"

οὐρανὸν noun accusative masculine singular "heaven"

εἰ conditional conjunction "if"

μὴ negative particle "not"

ὁ definite article nominative masculine singular "the"

ἐκ genitive preposition "from/out of"

τοῦ definite article genitive masculine singular "the"

οὐρανοῦ noun genitive masculine singular "of heaven"

καταβάς aorist active participle nominative masculine singular from καταβαίνω (I go down) "having gone down" (predicate position participle with temporal clause indicating action prior to the action of the main verb of the clause)

ὁ definite article nominative masculine singular "the"

υἱὸς noun nominative masculine singular "son"

τοῦ definite article genitive masculine singular "the"

ἀνθρώπου noun genitive masculine singular "of man"

ὁ definite article nominative masculine singular "the"

ὢν present active participle nominative masculine singular from εἰμί (I am) "one being"

ἐν dative preposition "in"

τῷ definite article dative masculine singular "the"

οὐρανῷ noun dative masculine singular "heaven"