Appendix.

Since the first Chapter dealt with the well-known charge-charge interactions familiar to biologists, this concluding Chapter introduces some key electrical forces, probably much less familiar, perhaps even unknown. LLPS (liquid liquid phase separation) which we have seen involved in so much of cell biology depends on multivalent, π-π and cation-π electrical forces. How these arise is dealt with here and may be especially useful as an aide memoir to return to when such issues arise within the bulk of the text.