Table 10.1 gives some approximate values for the atomic composition of a cell. The atomic composition represents a highly reductionist view, somewhat akin to asserting that the informational content of Macbeth is — Σaipnabec p i 1og2p i , where p i is the normalized frequency of occurrence of the ith letter of the alphabet. The next stage of complexity is to consider molecules (tables 10.2 and 10.3). This is still highly reductionist, however—it corresponds to calculating Shannon entropy from the vocabulary of Macbeth. Words are, however, grouped into sentences, which in turn are arranged into paragraphs. The cell is analogously highly structured—molecules are grouped into supramolecular complexes, which in turn are assembled into organelles. This structure, some of which is visible in the optical microscope, but which mostly needs the higher resolution of the electron microscope, is often called ultrastructure. It is difficult to quantify, i.e. assign numerical parameters to it, with which different sets of observations can be compared. The human eye can readily perceive drastic changes in ultrastructure when a cell is subjected to external stress, but generally these changes have to be described in words.