Any expert in electromagnetic fields? help-please

Indigo · Joined: 13 Feb 2006 Posts: 1

Hello everyone. i have very limited knowledge about electromagnetic fields and microwaves, the only technology related to this field which im a bit familiar with is MRI (Magnetic Resonance Imaging) which i rarely use when i try to identify some chamicals.
i'm mostly into the pharmaceutical industry, design of reactors and pharmaceutical plants/processes. i am also involved in Monoclona antibodies and Tissue Engineering productions which is a very exiting field as well.
going back to MRI, i'd be grateful if someone could give me a simple explanation of the mechanism as i know how to use the device and get the chemical composition of uknown compounds, but i do not know how does the device creates these different magnetic fields shown on the histogram.

Thank you so much for your help.