In our proposal we aim to explore and study the formation and distribution of magnetic clusters and their dynamics as a function of temperature in La0.85Sr0.15CoO3 using SANS measurements. The proposed material belongs to the spin glass regime which undergoes a glassy transition at low temperature. From our magnetization measurements an unusual magnetic phase called Griffiths phase is observed well above this temperature. Using Brillouin function we have modeled and simulated the magnetic cluster evolution and its distribution in the Griffiths phase. In this context SANS measurements are essential for the independent and accurate estimation of the spin cluster size and the fraction of spins participating in cluster formation in Griffiths phase.Keywords: Griffiths phase, cluster size, spin dynamics, SANS, single crystals