Natural hybridization is a frequent phenomenon among vascular plants. Hybridization is considered an important evolutionary force since it may lead to (1) an increase of the intraspecific genetic diversity of the participating populations, (2) the creation of new species, (3) species extinction through genetic assimilation, and (4) the generation of highly invasive genotypes. Because of the importance of plant hybridization in evolution, it is of great importance to accurately identify hybrid individuals. In this review, we give a general historical background of the study of plant hybridization. Also, we review some of the tools employed for hybrid recognition and their pattern of expression in hybrid individuals (morphological, chemical, chromosome number, and DNA fingerprinting techniques). We emphasize that even when chromosome number, morphological characters, and chemical characters are of limited use for hybrid recognition in the absence of DNA fingerprinting techniques, their exploration may give insights of the ecological performance of hybrids. This is of special importance when hybridization leads to evolutionary novelty in the form of polyploidy, transgressive character expression, or the expression of new secondary metabolites not present in the parental species.