Traditionally, carbohydrates (sugars) have been recognised as having roles in the provision and storage of energy, as structural units, and as being backbone components of 'more important' biological units such as the nucleotides. They have also, however, far more intricate and delicate roles to play in the areas of biological interactions and information transfer. Increasingly, their roles in receptor interactions, between cells, and between cells and other biological materials and microbes, are becoming better understood.