Phosphatidylinositol 3 kinases catalyze the phosphorylation of phosphatidylinositol (PI), or specific mono or bisphosphate derivatives of PI, at position 3 on the inositol ring to generate PI3P, PI(3,4)P[[2]] or PI(3,4,5)P[[3]]. The resulting phosphoinositides can act as signalling molecules to mediate/regulate a range of cellular and physiological processes, including cell polarity, cell migration, autophagy, growth, development, and ageing. (Adapted from FBrf0227909.)