Salam everybody, Graphviz is open source graph visualization software. Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks. It has important applications in networking, bioinformatics, software engineering, database and web design, machine learning, and in visual interfaces for other technical domains. I was looking for a software to draw a diagram for paths of reactions (each molecule/atom/radical as a node and reactions as an arrow between them), and finally I found it. It uses a very simple scripts, but very flexible. Official Webpage: http://www.graphviz.org/ (use the gvedit.exe file as the start and also you can use each diagram in the Gallery section of website by click on it and view its script.) Good luck, Hedayatzadeh