Comparing results from different methods must be approached with caution: particle size distributions reported in terms of volume, number or scattering intensity usually produce vastly differing results, despite the data having been derived from exactly the same physical material. Alongside particle size, another fundamental colloidal characteristic is zeta potential, which can also be measured rapidly using light scattering techniques. This effectively quantifies the parameter controlling electrostatic stabilization, and can be used in formulation development to avoid the instability that can result from particle-particle attraction.