Jains did not “discover” microorganisms in a modern scientific way (with microscopes), but Jain āgamas and later texts clearly speak about countless sūkṣma jīva (very tiny living beings) long before microbiology.

I’ll break your question in two parts:

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1. When and how did Jains know about micro‑organisms?

Scriptural idea (not lab discovery)

• From the time of the Tīrthaṅkaras (in our era, Bhagwan Mahāvīr: 6th century BCE), Jain teachings say:

- “In a drop of water there are countless living beings.” - Life exists in earth, water, fire, air, plants, as well as visible animals and humans.

• These are called ekendriya jīva (one‑sensed beings) and nigod/nigoda etc. – extremely minute, almost always invisible life-forms.
• The knowledge comes through keval‑jñāna (omniscience) of the Tīrthaṅkaras, then preserved in scripture and commented on by Ācāryas – not through physical instruments.

So, from a Jain point of view:

• Micro‑life was known by omniscience and scriptural revelation,
• Not “discovered” in a particular historical year by experiment.

Modern science much later (17th–19th century) used microscopes to confirm that water, soil, etc. are full of life – which nicely matches what Jain texts already described. You can see a simple discussion of “Jainism and microbiology” here:

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2. How did they know where micro‑organisms live?

Jain scriptures give systematic lists of where subtle jīvas exist:

(a) Five “body‑types” (kāyika jīva)

1. Pṛthvīkāy – earth‑bodied beings

- In soil, clay, stone, dust, mountains, etc.

1. Apkāy / Udak jīva – water‑bodied beings

- In every form of natural water: drops, ponds, rivers, etc.

1. Teukāy (Agni‑kāy) – fire‑bodied beings

- In flame, embers, hot fire, etc.

1. Vāukāy – air‑bodied beings

- In winds, air, atmosphere.

1. Vanaspati‑kāy – plant‑bodied beings

- In trees, grass, leaves, grains, roots, etc. - Also “sādhāraṇa vanaspati” (common, multi‑soul plants with many jīvas in one body, like roots, tubers).

These are mostly invisible to the ordinary eye, but are still living souls in Jain ontology.

The popular Sāth Lakh Sūtra lists the many types of jīva in different bodies, showing how detailed this mapping is. You can see this sutra and its simple explanation here:

(b) Nigod / Nigoda jīva

• Nigod jīva are described as:

- Infinitely tiny, extremely undeveloped souls, - Existing in clusters, - Filling all spaces where conditions allow life.

• Most souls spend enormous time in nigod-state, and only very few rise to more developed forms.

More details here:

(c) Practical rules that reflect this knowledge

Because Jains believe there are countless subtle jīvas:

• Water

- Is filtered, and for monks usually boiled and used within a time limit, because new jīvas arise if kept too long. - This assumes micro‑life in each drop of water. Related Q&As: – Why boiled water: – Boiling vs killing microorganisms: – Udambhi hiṁsā (violence to water‑bodied beings):

• Soil and roots

- Uprooting roots (like potatoes, onions etc.) is discouraged because it disturbs countless soil and root‑living micro‑jīvas. See:

• Fermentation / curd

- Fresh, carefully prepared curd may be allowed; stronger fermentation (old curd, yeast foods) is avoided because of heavy proliferation of micro‑jīvas. See:

These detailed rules make sense only if you assume a dense presence of unseen life in water, soil, plants, air, etc.

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3. Summary in simple words

• Jains did not “discover germs” with tools;

they affirmed the existence of countless invisible living beings through the spiritual knowledge of Tīrthaṅkaras, recorded in scriptures over 2500 years ago.

• They knew where micro‑organisms live by:

- Classifying jīvas into earth‑bodied, water‑bodied, fire‑bodied, air‑bodied and plant‑bodied, - Teaching that everywhere in nature – in water, soil, air, roots, plants, heat – there are living souls, often too small to see.

• Daily Jain practices (boiled water, filtering, avoiding roots, caution with fermentation) are all based on this long‑standing belief in micro‑life everywhere and the effort to practice ahiṁsā even towards these tiniest beings.