The manual handling of solutions (known as “beaker chemistry”) remains the Achilles Heel of modern analytical instrumentation. It is currently being replaced by flow injection analysis (FIA), which is computer compatible and allows automated handling of sample and reagent solutions with a strict control of reaction conditions. The flow injection analysis (FIA) was preceded by the success of segmented flow analysis, mainly in clinical and environmental analysis. This advance, as well as the development of continuous monitors for process control and environmental monitors, ensured the success of the FIA methodology. The fast and intensive development of the FIA methodology was due to several factors essential for routine analytical determinations, such as very limited sample consumption, the short analysis time based on a transient signal measurement in a flow-through detector and an on-line carrying out difficult operations of separation, physicochemical conversion of analytes into detectable species. On this field, Flow injection analysis offers unique features and advantages. FIA is therefore a mature technique with well-defined and explored principles of operation.