These two paragraphs are some notes from Daniel Ingram in his excellent (and free) book, Mastering the Core Teachings of the Buddha (with some very minor edits from me):
“For those who are practicing meditation (as opposed to experiencing an occurrence in daily life), in the early part of this stage, the meditator’s mind accelerates more and more, and reality begins to be perceived as particles or fine vibrations of mind and matter, each arising and vanishing utterly at tremendous speed. The traditional texts call this stage the beginning of insight practice, as from this point on there is a much more direct and non-conceptual understanding of the three characteristics...
This stage is marked by dramatically increased perceptual abilities when compared with the previous stages. For example, we might be able to hone our awareness to laser-like precision on the tip of our little finger and seemingly be able to perceive the beginning and ending of every single sensation that made up that finger.”
If that makes any sense and you want to know more about it, the printed book version of his book is here on Amazon, and you can also read the free HTML version of this book at this link.