Standardization of sampling, denominations, specifications (including safety requirements), marking and test methods allowing the verification of product claims for plant biostimulants, including microorganisms. Plant biostimulants are products based on substances and/or microorganisms, stimulating plant nutrition processes independently of the product’s nutrient content and defined by agronomical claims (e.g.: nutrient use efficiency, tolerance to abiotic stress, crop quality traits) and may be applied to plants or soils. Excluded are plant protection products, fertilizers, liming materials, soil improvers, growing media, and inhibitors that are already covered by standardization at European level.