A process to convert a pigment to finely-divided form comprises injecting crude pigment and/or prepigment suspension into a microjet reactor through jets onto a common collision point in a reaction zone. Pigment is converted to finely-divided form by: (1) injecting a suspension of coarsely crystalline crude pigment and/or hardly dispersible prepigment into a microjet reactor through jets onto a common collision point in a reaction zone in a housing; (2) introducing gas or vaporizing liquid to maintain a gas atmosphere in the reaction zone; and (3) removing the pigment suspension and gas/vapor by excess pressure on the gas inlet side or low pressure on the product and gas outlet side.
