The time period usually elapsing between the attainment of supersaturation and the appearance of the first crystals is called the induction time. It is considerably influenced not only by the initial conditions and process conditions, like supersaturation, state of agitation, temperature and seeding, but also by the measurement techniques used. The first changes in the system's physical properties due to the formation of the solid phase may be followed by the appearance of the first visible crystals. The measured induction time is generally a complex quantity made up of several components. It is often measured by visual observation or by particle size analyzer. Induction time varies within a large range (< 5 s up to 1000 s), at high supersaturation it can be very short, i.e. less than 1 sec.