How To - ELISA - Methods in Biochemistry
This is a method very commonly used in labs and the mandatory practical class for Biochemistry.
It is based on an enzymatic interaction between antibodies and the kind of substance you want to detect;
almost everything is possible - proteins like antigenes and viruses, hormones, and other organic material can be traced with this method.
Below with the green color, you see what a finished ELISA looks like. Some of the s.c. Eppendorf tubes are heavier on the green, while others don't show any kind of color reachtion at all:
In the following picture you can see how the process works as ELISA sandwhich method (the indirect identification of a substance):