Full Idea
The least corpuscle is actually subdivided ad infinitum and contains a world of new created things, which this universe would lack if this corpuscle were an atom.
Gist of Idea
Things are infinitely subdivisible and contain new worlds, which atoms would make impossible
Source
Gottfried Leibniz (Letters to Samuel Clarke [1716], 4.PS)
Book Reference
Leibniz,Gottfried: 'Philosophical Writings', ed/tr. Parkinson,G.H.R. [Dent 1973], p.220