An engineered extended ketocarotenoid pathway in rice and maize will be used as an example to illustrate how synthetic biology principles and multi-gene transfer can result in the formation of new molecular entities with useful biological properties.The creation of specialized novel sequestering structures facilitates the accumulation of metabolic precursors which can subsequently be decorated be different ketolases and hydroxylases to produce diverse combinations of ketocarotenoids in an organ-or tissue-specific manner.The quantitative and qualitative carotenoid and ketocarotenoid profiles of particular transgenic lines depend on the expression of the integrated transgene complement.Thus the generation and characterization of a combinatorial transgenic population is a pre-requisite to select specific lines with particular chemodiversity.We will discuss the fundamental mechanisms that underpin these experiments and we will highlight animal feeding trials to demonstrate the effects of diets fortified with particular combinations of target metabolites on products derived from such animals.