Natura - nature actualia - actual entities Mundus Plinius - physical world naturalia - natural bodies "crystal-kingdom" chemical substances chemical compounds Class carbohydrates [Cn(H2O)n, etc.] Class saccharides Class monosaccharides - sugars Class aldoses [H[CH(OH)]nC(=O)H (n>=2), etc.] glyceraldehyde [C3H6O3; CH(=O)CH(OH)CH2OH] 1 Stereoisomer D-glyceraldehyde [C3H6O3; CH(=O)CH(OH)CH2OH] 2 Stereoisomer L-glyceraldehyde [C3H6O3; CH(=O)CH(OH)CH2OH]