Users can easily import structure-related data into Chimera in the form of attributes, or values associated with atoms, residues, or models. The data can be imported with Define Attribute and then represented visually with color ranges, atomic radii, or "worm" thickness. Such data can also be manipulated programmatically in Chimera, and in fact Chimera was designed with extensibility and programmability in mind. It is largely implemented in Python, with certain features coded in C++ for efficiency. Python is an easy-to-learn interpreted language with object-oriented features. All of Chimera's functionality is accessible through Python and users can implement their own algorithms and extensions without any Chimera code changes, so any such custom extensions will continue to work across Chimera releases. Many programming examples are provided to assist extension writers.

The image shows interactions of the delta-1 loop with the rest of hepatitis C virus RNA-dependent RNA polymerase (Protein Data Bank entry 1quv). Loop residues in contact with the rest of the structure (van der Waals overlap ≥ 0.01 Å) are displayed as sticks; interacting surface atoms are shown as red patches. (More samples...)