How does reincarnation really work? It is not necessarily instantaneous because "ACTIVE" life is extremely very rare in the material universe.

Reincarnation or the transmigration of the jiva-soul, is not necessarily instantaneous. 

Reincarnation (the transmigration of the jiva-soul) depends on the availability of the next suitable deserved material bodily vessel being found, that could take millions of humans years to find because "life" in the material creation is extremely rare.

The fact is, "ACTIVE" life in a material bodily vessel in the material world, is extremely rare to achieve.

This means at the time of the death of the present material bodily vessel, the jiva-soul within that material body, may have to wait dormant until an appropriate material bodily vessel is found to enter.

Of course, the jiva-soul enters another material bodily vessel when its present one wears (dies) however, that could take millions of human years of waiting for an appropriate material bodily vessel for one to successfully transmigrate too.

Actually, life in the material creation is extremely rare, even today in nearly 2024, modern science have NOT found life outside planet Earth.

All this is due to the "active" life force or individual jiva-soul being able to enter life's 8 million 400 thousand species of bodily vessels that are extremely very rare throughout the material universes.

"Sarva-gatah" means life in the material universe is everywhere however, 99% of that life (jiva-souls) are "inactive" (dormant) within both the  impersonal brahmajyoti and the material atom- 

Tamala Krsna - "But within each atom the living entity (jiva-soul) is present?"

Srila Prabhupada - "Yes, God is present; therefore jiva-soul is present." 

Rupanuga - "So Paramatma (Visnu) and jiva-soul are ALWAYS together."

Srila Prabhupada - "Yes." (Morning Walk, April 4, 1975, Mayapur)

Or the jiva-souls are dormant (inert) in impersonal brahmajyoti.

The fact is, "less than 1%" of jiva-souls are "active" within a material bodily vessel within the 8 million 400 thousand species of life living "actively" on planetary systems existing inside the unlimited Brahmanda universes.

Just on our earth planet, there are only 8 billion human beings where as there are approximately 450 billion birds and 20 quadrillian (a billion, billion) animals on this earth planet. And numbers greatly expand in the lower species of like (insect, aquatic, plant, bacterial) 

So clearly, having the human form of life is very, very, very rare.

The fact is, by far, the majority of jiva-souls are hovering dormantly (inactively) in the impersonal Brahmajyoti, or are inert (almost dead) within EVERY material atom.

Therefore, Krsna's expansion Visnu (Paramatma or Supersoul) is in the atom, meaning the jiva-soul is also there in a "dormant" inert condition.

Ksirodakasayi Visnu (Paramatma or Supersoul) and the individual jiva-soul is within every atom, so there are individual jiva-souls EVERYWHERE in the material world. 

The Sanskrit for that is "sarva-gatah" which means life is EVERYWHERE but most are inactive or dormant within the brahmajyoti and material atom as explained above.

Tamala Krsna - "Srila Prabhupada, someone asked a question the other day about the atom which I couldn't give the answer to. His question is that if we say that within the atom the living entity, the jiva, is present, and life symptoms means six symptoms of birth, growth..."

Srila Prabhupada - "That's all right. Their life symptoms has not yet come. But there is."

Jayadvaita - "Potential."

Srila Prabhupada - "Yes."

Tamala Krsna - "His question was... It was sort of a dual question. At what time, or what...? Just like at the time of disintegration of this body, the living entity leaves this body and the body disintegrates, so does the atomic body also disintegrate when the living entity leaves it and moves to a higher body?"

Srila Prabhupada - "Atomic body? Atomic body means material body. Unless you are free from this material body, the atomic body will go on with you. That means unless you are mukta, the atomic body will go on. Mind, intelligence, ego — they are also atomic, finer atomic body."

Tamala Krsna - "But within each atom the living entity (jiva-soul) is present?"

Srila Prabhupada - "Yes, God is present; therefore jiva-soul is present."

Tamala Krsna - "So the living entity is present within the atom just as I am present within this body. When I leave this body, my body breaks apart."

Srila Prabhupada - "Yes, you leave this body, enter another body."

Tamala Krsna - "Right."

Srila Prabhupada - "By nature's law."

Tamala Krsna - "And when I leave this body, the body breaks apart."

Srila Prabhupada - "Eh?"

Tamala Krsna - "When I leave this body, the body dis... "

Srila Prabhupada - "The body is already atomic combination."

Tamala Krsna - "Yes."

Srila Prabhupada - "So it remains atomic combination. You leave the body."

Tamala Krsna - "Yes, it remains..."

Srila Prabhupada - "You leave the house. That does not mean the house is finished."

Tamala Krsna - "Right, I can understand that."

Hamsaduta - "He's asking that if the jiva-soul leaves the atomic particle, then does the particle break apart, isn't it?"

Srila Prabhupada - "No, no. You have not left atomic particle."

Tamala Krsna - "No, but you, you're... I think you were saying that within the atom there's also a living entity. So when that living entity leaves the atomic particle does the particle break apart? Or doesn't it? I mean what...?

Srila Prabhupada - "Just try to understand, from the sastra, you understand that andantara-stham: "God lives within the atom."

Tamala Krsna - "Yes."

Srila Prabhupada - "And when the God is there, living entity's also there. This... This much you try to understand. Because God and living entity, they remain together, as two friends. God is trying to save this fallen friend. That is the information from Upanisad. So when God is there, the living entity is also there."

Rupanuga - "So Paramatma (Visnu) and jiva-soul are always together."

Srila Prabhupada - "Yes."

Tamala Krsna - "Can we say that the living entity (jiva-soul) is present within the atom by consciousness?

Srila Prabhupada - "Hm? No, consciousness will gradually develop according to the bodily situation."

Pancadravida - "How does the jiva-soul get out of the atom and take a gross body?"

Srila Prabhupada - "Hmm?"

Pancadravida - "How will that jiva-soul..."

Srila Prabhupada - "(laughing) Body is combination of atoms. How he gets out of the atom. Body is nothing but combination of many atoms. Everything material is combination of many atoms. That's all."

Pancadravida - "The jiva-souls inside the atom, are they like impersonalists who are in the Brahman?"

Srila Prabhupada - "That you consider. He has not developed his consciousness. Practically, it is like dead." (Morning Walk, April 4, 1975, Mayapur).×^×.