Macromolecular engineering includes: rational design of the macromolecular structure including chain size, uniformity, topology, microstructure (sequencing and tacticity), composition and functionality; precise synthesis with high selectivity at reasonable cost, both in effort and environmental impact; assembly of macromolecules to supramolecular objects via controlled processing, including temperature, pressure, solvents, mechanical stresses, etc.; detailed characterization of the prepared materials at both molecular and macroscopic level; modeling of polymerization and processing conditions to aid in the design of appropriate conditions to reach targeted properties and function, and optimization of the entire process. Some recent unprecedented advances in control over various polymerization systems, including ionic, radical, coordination and even polycondensation have enabled synthesis of many new well-defined (co)polymers and some of them are briefly discussed. Precise control of various aspects of macromolecular architecture, including topology, functionality and microstructure have been achieved both in homogeneous and heterogeneous polymerization system and applied to preparation of polymeric hybrids, conjugates and other functional materials. The well-defined (co)polymers self-assembly or can be pre-assembled to materials with precisely controlled morphologies which can be affected and fixed by processing. The final macroscopic materials properties depend on molecular structure of (co)polymers and can be rationally retro-designed.