A flower is, to a morphologist, simply a highly condensed shoot built specifically for sexual reproduction, arranged as four concentric whorls around the floral axis (pedicel) - the calyx (sepals) and corolla (petals), which are chiefly protective and attractive, and the androecium (stamens) and gynoecium (pistils), the two essential reproductive whorls. Sexual reproduction itself rests on gametogenesis (production of gametes) and fertilization (their fusion); in lower plants such as algae and bryophytes this fertilization is external and the gametic fusion may be isogamous, anisogamous or oogamous, whereas in higher (flowering) plants fertilization is internal, and unfolds across three sequential stages treated across this chapter - pre-fertilization structure and events, fertilization, and post-fertilization structure and events. Understanding of this internal, flower-based reproductive system was built up gradually: Nehemiah Grew (1682) first identified the stamen as the male organ and R.J. Camerarius (1694) described the anther, pollen and ovule; J.G. Kolreuter (1761) documented insect pollination; G.B. Amici (1824) discovered the pollen tube; Hofmeister (1848) described the structure of the pollen tetrad; Hanstein (1870) traced embryo development in Capsella and Alisma; Strasburger reported polyembryony (1878) and discovered syngamy (1884); Nawaschin and Guignard (1898-99) independently discovered double fertilization, unique to angiosperms; and later work extended this into embryo culture (Hanning, 1904), a formal classification of embryo development (Johansen, 1950), experimental haploid production from pollen (Guha and Maheswari, 1964), the genetic ABC model of floral organ identity (Coen and Meyerowitz, 1991) and a modern molecular synthesis of the whole field (Krishnamurthy, 2015). The eminent Indian botanist P. Maheswari (Panchanan Maheswari, 1904-1966) specialised in exactly this field - plant embryology, morphology and anatomy - becoming a Fellow of the Indian Academy of Science in 1934, publishing 'An Introduction to the Embryology of Angiosperms' in 1950, and founding the International Society of Plant Morphologists in 1951.