Once that primary needs are satisfied, mankind utilises plants for different applications. First, the precious molecules given by nature are extracted using methods such as distillation or maceration. They are used for health (pharmaceuticals or traditional medicine), well-being (essential oils), or for decorative purposes (pigments). This method is called the deconstruction approach. It can be completed by chemical modification, yielding hemisynthetic products such as modified starch or cellulose acetate. On the other hand, plant material can be cracked to obtain simple molecules. For instance, gasification of biomass leads to CO, H2, CH4, etc. These molecules can enter the traditional synthetic routes widely developed by the petrochemistry to form more complex compounds for a large variety of products. In any case, the deconstruction or the cracking approach should take into account the green chemistry principles and be the object of a life-cycle assessment. Bio-based products are not necessarily good for the environment, or more precisely, they might have a bigger impact on the environment than the fossil alternative. This chapter demonstrates through a few examples that smarter and more sustainable solutions always exist. The advantages of biomass and the big principles to a sustainable approach of the biomass valorisation are given.