Multiphase flow reactors are heart of many process industries. However, the flow dynamics of these reactors are not well understood mainly because of complex flow physics involved. In this course different technique available for monitoring and mapping of multiphase flow reactors will be discussed in detail. Techniques will be divided in two parts: Invasive, in which some probe will be intruded inside the vessel to measure the velocity and/or phase fraction and in Second part non-invasive techniques will be discussed in which measurement will be performed without disturbing the flow. The basic principle, equations, post processing methods, advantages and limitations of each technique will be discussed in detail.