Animation recorded with the Bloch Simulator showing how resonant radiowaves that push (as shown by the red bar) the magnetization (white) in synchrony with the natural precession can rotate it away from equilibrium.

Free educational MRI sofware version 3.1 is available for Windows, Mac and Linux. Easy to install and use. The software is described in RadioGraphics (Reviewer1: "Very nicely done...". Reviewer2: "...help greatly during classroom presentations of MRI basics and applications..."). Version 3.1 offers much improved visualization of magnetic resonance phenomena via support for an add-on, open-source OpenGL viewer that exploit the capabilities of modern 3D graphics cards. Click for info, example animations and download.