This short review emphasizes the importance of secreted molecules (peptides, proteins, arabinogalactan proteins, PR proteins, oligosaccharides) produced by cells and multicellular structures in culture media. Several of these molecules have also been identified in planta within the micro-environment in which the embryo and endosperm develop. Questions are raised about the parallel between in vitro systems (somatic and androgenetic) and in planta zygotic development. A view of exchanges between embryonic and nonembryonic multicellular structures in vitro is presented, and several facts about embryo and endosperm molecular interactions in planta are reported. Analysis of in vitro mechanisms may help in understanding what happens during zygotic embryogenesis.