Chemical space is a core concept in chemoinformatics , which refers to all molecules as well as multidimensional conceptual space. In contrast, the universe includes all types of matter and energy; galaxies; solar systems; and all the contents of the space that could be called cosmic space, which means the entire universe. Unlike cosmic space, chemical space is dependent on the structural representation and the type of properties or descriptors used to represent the compounds of interest. For example, the types of descriptors employed to represent small organic molecules will be different than those describing organometallic molecules, and both constitute a fraction of the chemical space .