This disclosure is drawn to systems, devices, apparatuses, and/or methods, related to milling particles in drilling fluid. Specifically, the disclosed systems, devices, apparatuses, and/or methods relate to milling particles in drilling fluid using multiple milling techniques. Some example apparatuses may include a first mill to grind particles from the original diameter to a first reduced diameter, and a second mill to grind the particles from the first reduced diameter to a second reduced diameter, where the second reduced diameter is less than the first reduced diameter.