There are two methods of blending: batch in-line blending and multi-header rundown blending. Batch in-line blending combines in-line and batch-blending. Batch in-line blending uses a single header while all blend components are proportionally and simultaneously conducted. On the other hand, multiple-header rundown blending has more complex processes. It involves many processing units to feed into rundown headers, multiple control rooms, process operators, and control systems. This topic will describe two methods of blending; their examples; and applications; offline, online, and regulatory blend control strategies; in-line blend certifications; etc.