Due to overconsumption of fossil carbon, humanity faces four major problems: global warming, decrease of biodiversity, pollution of the biosphere, and the degradation of agriculture soils. It is not enough to reduce our greenhouse gas emissions by stopping the consumption of fossil carbon; it is also urgent to remove carbon dioxide from the atmosphere. In order to understand the challenges outlined above, a minimal knowledge of the most important carbon compounds and their transformations is an asset. This textbook is therefore an introduction to the molecular sciences and shows how we depend on carbon compounds, what they are and how they are transformed. Plant biomass, including agricultural, forestry and urban wastes, is the source of bio-carbon that can replace fossil carbon. In addition, we will always need carbon-containing substances for our comfort and health. These important topics are covered in this textbook. Life begins with water, carbon dioxide, and the sun. Carbon dioxide is not a waste, but a starting material for a better life. Biomass and carbon dioxide are our best allies in sustainable development (circular economy). This textbook explains why.