FIELD VALUES SHOWN BY OBJECT COLOUR In many fields of science one would like to display values defined at every point in a volume of space. Examples are the temperature throughout a room, or the density of gas through a cloud. The examples here show the electric potential round a molecule. The molecule in question is enalapryl. This is of interest because it has the effect of reducing the blood pressure. A number of such drugs are known and a study was carried out to determine if the effect could be related to their electric fields. This might give a lead to designing new drugs which are more effective. The pictures show the electric field of the molecule by colour. Red represents negative potential, green neutral and blue positive. (This is diferent from the battery terminal colours, but tends to cause oxyygen atoms to be coloured red and nitrogen blue in conformance with normal convention). The molecule in conventional colours is shown at the top left. (White are carbon atoms, red oxygen, light blue hydrogen, dark blue nitrogen and yellow are sulphur). The top right shows it surrounded by a semi-transparent sphere coloured according to the electric potential. The bottom left shows the potential at the surface and extending out into space. The bottom right picture shows the potential within the molecule.