Being an ‘underpinning technology’, fluid flow closely reflects and sometimes precedes
the developments of the ‘core technologies’ of the time. Only in the second half of 19th
century that the term ‘two-phase flow’ was pronounced and added as a chapter to fluid
mechanics and unit operations books. At that time, two-phase flow term was used predominantly to denote gas–liquid flow, which is not coincidental, as the leading technologies were nuclear and thermal, addressing mainly vapor–liquid systems. Development of
secondary and tertiary oil recovery technologies in 1980s focused the attention of the scientific world on surfactants and liquid–liquid systems incorporating surfactants. The new
millennium brought with it a vision toward a change in the scale of processes and dimensions from macroscale to microscale. Along with it came the need for a fundamental
understanding of processes in the molecular scale, in place of empirical models