This paper is devoted to computer modelling of the development andregeneration of multicellular biological structures. Some species (e.g. planaria andsalamanders) are able to regenerate parts of their body after amputation damage, butthe global rules governing cooperative cell behaviour during morphogenesis are notknown. Here, we consider a simplified model organism, which consists of tissuesformed around special cells that can be interpreted as stemcells. We assume that stemcells communicate with each other by a set of signals, and that the values of thesesignals depend on the distance between cells. Thus the signal distribution characterizeslocation of stem cells. If the signal distribution is changed, then the difference betweenthe initial and the current signal distribution affects the behaviour of stem cells—e.g.as a result of an amputation of a part of tissue the signal distribution changes whichstimulates stem cells to migrate to new locations, appropriate for regeneration of theproper pattern. Moreover, as stem cells divide and form tissues around them, theycontrol the form and the size of regenerating tissues. This two-level organization of themodel organism, with global regulation of stem cells and local regulation of tissues,allows its reproducible development and regeneration.