Mathematics has successfully been applied to understand physics, but its application to biology and medicine is still developing. While early attempts at mathematical formalization of biology lacked biological substance, the situation has improved in recent decades. In medical imaging, mathematical approaches can be used to understand image data and make inferences about organs. One promising approach models growth as random iterated diffeomorphisms in biologically meaningful "darcyan coordinates". This allows modeling of growth through discrete cellular decisions over time and derivation of differential equations describing growth in the limit. Further developing the biological basis and applying these methods to real medical data offers opportunities to advance the role of mathematics in understanding biology and medicine.