Numerous plant species are known to express one or more lectins or proteins containing a lectin domain, enabling these proteins to select and bind specific carbohydrate structures. The group of plant lectins is quite heterogeneous since lectins differ in their molecular structure, specificity for certain carbohydrate structures, and biological activities resulting therefrom. This chapter presents a short historical overview on how plant lectin research has evolved over the years from a discipline aiming merely at the purification and characterization of plant lectins towards the application of plant lectins as tools in glycobiology.