Hi Enrico, Any Chimera actions can be done with python, but I can't give advice on that (I don't know python). To me, it seems much easier to use a few Chimera commands than to figure out the python to do the same things. From what you said, now I think maybe you are making a movie, not just trying to superimpose structures to prepare for morphing. In that case, here is how you could easily achieve complicated motions of multiple models: use the command "savepos" to save different positions, say one position with the models together and another with the models apart. Then you can use the command "reset" to go between these saved positions in a specified number of frames. Depending on those previously saved positions, the (two or more) models could go in opposite directions. For movie making, I recommend using version 1.4 of Chimera (a daily build) because many of the movement commands have been improved significantly since the last production release. See: <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/savepos.html> <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/reset.html> <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/fly.html> <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/ movies.html#moviecommands> I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html