Why do some animals regenerate, while others do not? Regeneration is one the greatest remaining mysteries of biology. Since animals that do and do no regenerate share the same set of signalling molecules and transcription factors, the difference in regenerative abilities must lie in the regulation of these genes. To understand these regulatory mechanisms, I study the regulatory dynamics of highly regenerative planarian flatworms. I am particularly interested in the regulatory mechanisms of regenerative polarity and positional. In other words, I study how adult planarian stem cells correctly proliferate, migrate, and differentiate according to their position along the body axis.