SB 12.7.12

puruṣānugṛhītānām
 eteṣāṁ vāsanā-mayaḥ
visargo ’yaṁ samāhāro
 bījād bījaṁ carācaram
Synonyms: 
puruṣa — of the Supreme Personality of Godhead in His pastime role of creation; anugṛhītānām — which have received the mercy; eteṣām — of these elements; vāsanā-mayaḥ — consisting predominantly of the remnants of past desires of the living entities; visargaḥ — the secondary creation; ayam — this; samāhāraḥ — manifest amalgamation; bījāt — from a seed; bījam — another seed; cara — moving beings; acaram — and nonmoving beings.
Translation: 
The secondary creation, which exists by the mercy of the Lord, is the manifest amalgamation of the desires of the living entities. Just as a seed produces additional seeds, activities that promote material desires in the performer produce moving and nonmoving life forms.
Purport: 

Just as a seed grows into a tree that produces thousands of new seeds, material desire develops into fruitive activity that stimulates thousands of new desires within the heart of the conditioned soul. The word puruṣānugṛhītānām indicates that by the mercy of the Supreme Lord one is allowed to desire and act in this world.