On the Buddhic plane we become one with the Universal Soul.
‘Their next step is to rise to the Causal plane, and there they receive the secret treasures of Wisdom; all the mysteries of the universe are revealed to them; they are allowed to see and contemplate all the beauty of the Heavenly regions. Later, they rise to the Buddhic plane where they become one with the Universal Soul and dwell in bliss beyond description.

As for the Atmic plane, words cannot express what they experience on this plane as they fuse into one with their Creator.

When humans reincarnate they pass through the regions in the opposite direction
When humans reincarnate they pass through all the same regions, beginning with the Atmic, Buddhic, Causal, and so on and, in each region, they collect the materials they need to weave a new garment, a new body, which becomes progressively denser and more opaque as they descend to the lower levels of matter.

When we are born we remember nothing of this but the knowledge is inside us
When they are finally born again, as a human baby, they remember nothing of all this: neither their sufferings nor their joys nor even what they learned. But it is all there, inside them, and it will all come back to them one day if they accept certain disciplines and rules of life under the guidance of a spiritual Master. Those who succeed in bringing to the surface the memory of their experiences in the other world evolve much more rapidly.

Some will not be satisfied with a mediocre life and will search for these treasures
Unfortunately, most people are so attached to the pleasures and passions of the earth that it will be a very long time before they take advantage of all this knowledge, all those treasures buried deep within them. Blessed are those who know and believe these truths, for they will be incapable of being satisfied with a mediocre way of life. They will continually want to grow and advance in intelligence, love and self-dominance, so as to become useful to the whole of humanity.’

Omraam Mikhaël Aïvanhov

The Seven Bodies of Man explanation

To be continued…

Complete Works Volume 32, The Fruits of the Tree of Life – The Cabbalistic Tradition
Chapter 15, Death and the Life Beyond