Communication between cells in an organism is an essential part in complex life. There are many forms of communication in both plants and animals, such as hormone signaling, nerve signaling, and so on. The main obstacle in cellular communication is the large distances between the cells themselves. In humans this is commonly remedied by the cardiovascular system, but plants very obviously don't have a heart. What they do have, however, is a system organized into ˜vascular bundles' throughout their stems. Within these vascular bundles are the two systems used for long distance transport: the xylem and the phloem. Structured in a circular fashion, the xylem lines the inner edge of the phloem. The phloem and xylem consists of elongated ˜sieve cells,' which are relatively void of organelles and nuclei, and tended to by companion cells. Water and nutrients from the roots are transported up to other parts of the plant via the xylem. This is not a system commonly used for cellular communication, though, for water and nutrients may only more up the xylem by the sort of vacuum created within plant vascular systems from water leaving the plant through the stomata, paired with the pressure by osmosis of water entering the roots. Where the real action happens is within the phloem. Studies into the phloem show that it carries out more than just transport; the phloem is more or less an "information superhighway  between cells. The trafficking of assimilates, viruses, RNA, plant hormones, metabolites, and proteins is conducted here, alongside the long known job of transporting the products of photosynthesis for storage either in fruits, tubers, or roots. Within the phloem, one can find small molecules such as peptides, proteins, nucleic acids, and lipids. What remained unexamined for a long time was the presence of lipids and lipid-binding proteins, as they were surprising discoveries within the aqueous environment within the vascular bundles.