The current theoretical atomodel involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Within the nucleus exist nucleons which consists of several very shortliving particles.
There were already several cosmological models and attempts to explain creation as consisting of the smallest particles in the past of mankind.
In the Samkhya, the Anu of the Maharloka stands for the first maya-afflicted primordial particle. Its creation happens by the interaction of the atmic light with the Maya, which also creates simultaneous a new time and a separate space.
Also the Nyaya assumes invariable atoms (Anu). Sri Yukteswar Giri has regarding this created a simplified diagram in his book "The Holy Science .
The Svetasvatara Upanishad, 1 describes the self as infinitely smaller than the hundredth part of a hundred times divided tip of a hair, and nevertheless unlimited in its extent.
The Srimad Bhagavatam says in 3.11.5 : aṇur dvau paramāṇū syāt, trasareṇus trayaḥ smṛtaḥ, jālārka-raśmy-avagataḥ, kham evānupatann agāta (... two atoms make one double atom, and three double atoms make one hexatom ...)
The Nyasa and the Vaiseshika also assumed Anu's with a size of one sixth of the smallest perceptible object.
The kashmiric trika calls the Trinity of Shiva, Shakti, and Anu. Anu is the limited atom or individual (sometimes also nara - man).
Kashyapa(also : Kaṇāda) and Pakudha Katyayana from the Vaisheshika developed a different doctrine. Kaṇāda saw Parmanu (atom) as an indestrutible particle of matter and indivisible and indestructible. It cannot be sensed through any human organ.
According to Kaṇāda, there are 4 sorts of atoms corresponding to the four physical elements of earth (prithivi), water (apa), fire (teja), and air (vayu). The fifth element is the no longer material ether (akasha), the carrier of the sound ether (shabda).
Beyond this is the subatomic parama-aṇu  as the smallest particle, which is spatially not tangible.
By assembly of two Paramanus arise the anuss (Skt. Atom) as the first spatially identifyable structures.
Leukipp formulated an átomos - theory with indivisible primordial particles , which his disciple Demokrit extended: Only apparently a thing has a color, it only seems to be sweet or bitter. In reality there are only atoms in the empty space.(Demokrit)
Aristotle [5;6]criticized this: The question of the movement, from where and where it comes to things, has also been put aside by You like by the others, without to rack Your brain.
Epicurus further expanded this doctrine .
In Buddhism, Dharmakirti described such an extremely short-lived energy particle (paramanu). Vasubandhu described 2 particles in the Abhidharmakośabhāṣya: dravya- and sanghata-paramanu. 
According to the Patthana belonging to the Pali canon, the four mahabhutas are for the upada rupas as the causative conditions (paccaya). The upada-dhammas emanate the rupa-dhammas.
Annie Besant, C.W. Leadbeater and Curuppumullage Jinarajadasa had 1908 in their book Investigations by Clairvoyant Magnification into the Structure of the Atoms of the Periodic Table and Some Compounds indicated, that the chemical structure can be seen by the so-called third eye.[9;10].