SB 2.10.30

nididhyāsor ātma-māyāṁ
 hṛdayaṁ nirabhidyata
tato manaś candra iti
 saṅkalpaḥ kāma eva ca
Synonyms: 
nididhyāsoḥ — being desirous to know; ātma-māyām — own energy; hṛdayam — the location of the mind; nirabhidyata — was manifested; tataḥ — thereafter; manaḥ — the mind; candraḥ — the controlling deity of the mind, the moon; iti — thus; saṅkalpaḥ — determination; kāmaḥ — desire; eva — as much as; ca — also.
Translation: 
When there was a desire to think about the activities of His own energy, then the heart (the seat of the mind), the mind, the moon, determination and all desire became manifested.
Purport: 

The heart of every living entity is the seat of the Supersoul, Paramātmā, a plenary expansion of the Supreme Personality of Godhead. Without His presence the living entity cannot get into the working energy according to his past deeds. The living entities who are conditioned in the material world are manifested in the creation in terms of respective inclinations inherent in them, and the requisite material body is offered to each and every one of them by the material energy under the direction of the Supersoul. This is explained in the Bhagavad-gītā (9.10). When, therefore, the Supersoul is situated in the heart of the conditioned soul, the requisite mind is manifested in the conditioned soul, and he becomes conscious of his occupation as one is conscious of his duty after waking up from slumber. Therefore the material mind of the living entity develops when the Supersoul sits on his heart, after which the mind, the controlling deity (moon), and then the activities of the mind (namely thinking, feeling and willing) all take place. The activities of the mind cannot begin without the manifestation of the heart, and the heart becomes manifested when the Lord wants to see the activities of the material creation.