When the cell number in suspension cultures is plotted against the time of incubation, a growth curve is obtained depicting that initially the culture passes through a lag. phase, followed by a brief exponential growth phase (the most fertile period for active cell division), and a decline in growth after three to four cell generations, indicating the stationary phase.

For a subculture the flask containing the suspension culture is stood still for a few seconds to enable the large colonies to settle down. A pipette or a syringe with an orifice fine enough to hold aggregates of two to four cells or only single cells is used.The suspension is taken from the upper part of the culture and transferred to a fresh medium.