We aim to use a simple model organism, the harmless nematode worm C. elegans to investigate how growth is controlled. Growth is a defining property of living organisms including humans. How fast we grow and to what size we grow are both influenced by both external factors such as the quality of our diet and by internal factors. Growth problems can cause serious disease in themselves and may underlie increased susceptibility to other problems such as heart disease. We have found that changes in a particular gene alter both the growth rate and size of the animal. This gene codes for part of the network of proteins that allow animals to transmit messages within cells using the simple molecule calcium. This signalling network is one of the most common and important signalling systems in animals and humans. Our aim is to discover how this system regulates growth by identifying which other genes are involved and where in the animal (in which cells or tissues) it acts. Using C. elegans will allow us to use state-of-the art genetic approaches on a large scale so that we can simultaneously test a large number of ideas about how the system might work and identify new components of the system. By doing this we will increase our understanding of growth regulation which in turn should help us to ensure that diseases caused by alterations in growth can be treated more effectively and that people can grow healthily.