Bhagavad Gita 7.4भूमिरापोऽनलो वायुः खं मनो बुद्धिरेव च।अहङ्कार इतीयं मे भिन्ना प्रकृतिरष्टधा ॥

This eightfold Nature constitutes the inferior Nature or Apara Prakriti. The five gross elements are formed out of the Tanmatras or rootelements through the process of Pancikarana or fivefold mixing. Tanmatras are the subtle rootelements. In this verse, earth, water, etc., represent the subtle or rudimentary elements out of which the five gross elements are formed.Mind stands here for its cause Ahamkara intellect for its cause the Mahat Ahamkara for the Avyaktam or the unmanifested (MulaPrakriti) united with Avidya which is conjoined with all kinds of Vasanas or latent tendencies. As Ahamkara (Iness) is the cause for all the actions of every individual and as Ahamkara is the most vital principle in man on which all the other Tattvas or principles depend, the Avyaktam combined with the Ahamkara is itself called here Ahamkara, just as food which is mixed with poison is itself called poison.