The present invention relates to processes and systems for preparing nanoparticles, cellular or viral membranes and/or cellular or viral membrane coated nanoparticles using or comprising, inter alia, a multi-inlet vortexing reactor, tangential flow filtration (TFF) and/or a high shear fluid processor such as a microfluidizer (or a microfluidizer processor). The present invention also relates to the nanoparticles, cellular or viral membranes and/or cellular or viral membrane coated nanoparticles prepared by the present processes and systems, and the uses and/or applications of the nanoparticles, cellular or viral membranes and/or cellular or viral membrane coated nanoparticles.