Don Kientzler Center for Pharma Crystallization, J-Star Research Inc 6 Cedar Drive, Cranbury, New Jersey 08512 Controlled crystallization of an API in submicron size was enabled based on an accurate solubility profile and a growth inhibition property via semi-continuous processing, to meet special formulation requirements. This process was also challenged by isolation of nano-API crystals to meet the low specification of residual salt content. When residual salt becomes too low, crystal growth accelerates. Diafiltration using membranes was applied for salt removal in connection to outstream of a flow-through CSTR for generation of submicron crystals, to deliver product meeting the specifications of both crystal size and the residual salt content.