What are monosaccharides made of

any of the class of sugars (e. g., glucose) that cannot be hydrolyzed to give a simpler sugar.

Carbohydrates (also called saccharides) are molecular compounds made from just three elements: carbon, hydrogen and oxygen. Monosaccharides (e. g. glucose) and disaccharides (e. g. sucrose) are relatively small molecules. They are often called sugars.