Source : Webster's Revised Unabridged Dictionary (1913)

Micella \Mi*cel"la\, n.; pl. {Micell[ae]}. [NL., dim. of L. mica
   a morsel, grain.] (Biol.)
   A theoretical aggregation of molecules constituting a
   structural particle of protoplasm, capable of increase or
   diminution without change in chemical nature.