The Miocene was the first epoch of the Neogene period (23-2.5 million years ago), followed by the much shorter Pliocene epoch (5-2.6 million years ago); both the Neogene and Miocene are themselves subdivisions of the Cenozoic Era (65 million years ago to the present). Climate and geography.
The dictionary meaning of the word Digress is 'to leave the main subject temporarily in speech or writing.' or simply deviate. As you say,I digress means  I am straying from the main subject right now. . Like in this sentence - 'I need to digress a bit to let the ink dry.'. Hope this helps :)
syn: deviate, digress, diverge imply turning or going aside from a path. To deviate is to stray from a usual or established standard, course of action, or route: Fear made him deviate from the truth. To digress is to wander from the main theme in speaking or writing: The speaker digressed to relate an amusing anecdote.