This book describe techniques that allow for direct quantification of carbon fluxes in large metabolic networks, include the use of C-13 labelled substrates and genome-scale metabolic models. This book also highlight the importance of such information for specific biological processes, including the ageing of cells, the immune system & organogenesis. The book concludes with a summary of recent advances in genome editing, which have allowed for precise genetic modifications, even with dynamic control of gene expression.