Nonlinear phenomena in a flowfield where chemical processes proceed are discussed from a chemical engineering viewpoint of how to design and precisely control complex chemical processes and systems. Two kinds of reactors are studied : continuous stirred tank reactor (CSTR) and Taylor vortex flow reactor (TVFR). After discussing the mixing characteristics of the flowfield, two kinds of complex chemical reaction systems are considered: the Belousov-Zhabotinskii (BZ) reaction and emulsion polymerization. The complex bifurcating behavior of chemical oscillations in the BZ reaction is demonstrated in a TVFR as well as in a CSTR. The mechanism for self-sustained oscillations in the continuous emulsion polymerization of vinyl acetate is also discussed. How to control the instability and its bifurcation of transport phenomena with/without chemical reactions should be reconsidered taking into account the effect of hysteretic multiplicity in the states of flow and reaction for the purpose of introducing the methodology of emergent synthesis into a design concept of complex chemical processes and systems.