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How did Anaxagoras explain the formation of different substances?

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Bronze bust of Epicurus with a full beard and draped clothing, displayed on a round inscribed base at the National Archaeological Museum of Naples. — Atomism Epicurus, bronze bust from a Greek original, c. 280–270 bce; in the Museo Archeologico Nazionale, Naples.

Anaxagoras explained the formation of different substances by proposing that the universe is composed of an infinite number of qualitatively distinct, eternal, and incorruptible particles, which he referred to as "seeds".12

Central to his system is the principle that "there is a portion of everything in everything". Every substance contains all possible kinds of these seeds, and a specific object is identified by the type of seed that predominates within it. Consequently, substances are not created or destroyed in the absolute sense; rather, they appear to change through the separation and commingling of these seeds.21

The organization of these materials was directed by nous (mind or reason), which initiated a revolving process that gathered "like to like," allowing specific substances to manifest in greater concentrations. This process accounts for the diversity of the physical world, as the extraction and rearrangement of these inherent seeds allow for the growth and transformation of all things, including biological matter like flesh, bone, and hair.2