Jmol. Jmol is computer software for molecular modelling of chemical structures in 3 dimensions. 
It is an open-source Java viewer for chemical structures in 3D.
The name originated from [J]ava (the programming language) + [mol]ecules, and also the mol file format. 

JSmol is an implementation in JavaScript of the functionality of Jmol. It can hence be embedded in web pages to display interactive 3D models of molecules and other structures without the need for any software apart from the web browser (it does not use Java).

Both Jmol and JSmol render an interactive 3D representation of a molecule or other structure that may be used as a teaching tool, 
or for research, in several fields, e.g. chemistry, biochemistry, materials science, crystallography, symmetry or nanotechnology.

Software
Jmol is written in the programming language Java, so it can run on different operating systems: Windows, macOS, Linux, and Unix, as long as they have Java installed. It is free and open-source software released under the GNU Lesser General Public License (LGPL) version 2.0. The interface in translated into more than 20 languages.

There are several products implemented:
 A standalone application (the Jmol application), composed of a single Jmol.jar file that can be used without installation, requiring only that the computer has Java installed.
 A software development kit (SDK), i.e. a component that can be integrated into other Java applications, such as Bioclipse and Taverna.
 JSmol, a JavaScript library that allows integration of the 3D models in web pages and wikis.

Molecules can be displayed in different styles of rendering, like ball-and-stick models, space-filling models, ribbon diagrams, molecular surfaces, etc.
Jmol supports a wide range of chemical file formats, including Protein Data Bank (pdb), Crystallographic Information File (cif and mmcif), MDL Molfile (mol and sdf), and Chemical Markup Language (CML). 
It can also display other types of files for structures with 3D data.

JSmol replaced the Jmol Java applet, which in turn had been previously developed as an alternative to the Chime plug-in, both of which became unsupported by web browsers. Jmol was initiated
to reproduce functions present in Chime (with the exception of the Sculpt mode) and has been continuously growing in features, surpassing the simple display of molecular structures. Most notably, it has a large set of commands and a thorough scripting language (JmolScript) that includes many characteristics of a programming language, such as variables, arrays, mathematical and Boolean operators, SQL-like queries, functions, loops, conditionals, try-catch, switch...

Screenshots

See also 

 Chemistry Development Kit (CDK)
 Comparison of software for molecular mechanics modeling
 List of free and open-source software packages
 List of molecular graphics systems
 Molecular graphics
 Molecule editor
 Proteopedia
 PyMOL
 SAMSON
 SMILES

References

External links 

 Demonstration of JSmol capabilities. A simple page with interactive demonstrations of several features of JSmol embedded in the page.
 Jmol website (Official website, though not fully up to date)
 Jmol Wiki (active and updated) with, among other information, listings of websites, wikis, and moodles

 
 Jmol extension at MediaWiki.
 Jmol extension for MediaWiki at SourceForge.
 Jmol extension for MediaWiki at JmolWiki.
 Proteopedia - Life in 3D, a collaborative and free 3D-encyclopedia of proteins and other biomolecules. (Uses Jmol Extension as a core component)
 Biomodel Complements for learning biochemistry and molecular biology.
 Molview

Chemistry software for Linux
Free chemistry software
Free software programmed in Java (programming language)
Molecular modelling software