Today I started reading the Italian version of The 21st Century Brain, Explaining, Mending and Manipulating the Mind, by Steven Rose, published by The Random House Group, 2005, London. The Italian version I am reading is translated by Elisa Faravelli and published in a special edition by the magazine Le Scienze with the permission of Codice Edizioni, Torino. I am still reading the second chapter, but I have already found some interesting points. The first interesting point is that cells must divide because of the limits imposed to their structures by the law of physics. A cell for growing needs to get nutrients from the outside environment and because the cell is separated from its environment by a membrane, the nutrients have to pass through this membrane in order to reach the cytoplasmic body of the cell. So if the cell needs a certain amount of nutrients to pass the membrane in given unity of time the membrane needs to be large enough to allow it. However the volume of body of the cell grows following the cube of the radius, while the surface of the cell grows following the square of it, so at a certain point its impossible for the membrane to provide enough nutrients for the body cell and the cell must divide in order to surivive. The second interesting point is about cooperation among cells in the developing of multicellular organisms. When more cells start cooperating and creating aggregations, they take advantage of a progressive specialisation: not all cells have to be able to do everything anymore. Well, when a cell works alone, it has to get signals from the environment and try to adapt to them, however when many cells are working together just some of them (those placed on the surface of the organism) get specialised in receiving signals from the outside world, while there will be other cells in charge of reacting to that signals and shaping the whole organism behaviour. This brings to the need of communication among cells. Summarizing:

one cell needs:	being able to read signals from the outside environment	diffusing signals inside its own body causing a reaction which hopefully will bring to a better adaptation to the environment	-
many cells need:	being able to read signals from the outside environment (both inside or outside the organism)	diffusing signals inside their own body causing it to react	exchanging signals with other cells causing them to react