According to string theory, matter is made up of strings.
The string-loop theory that might finally untangle the universe
Symmetry is a Guide to Reality
String Theory Explained : r/Physics
Michio Kaku Shares About His Lifelong Quest for a 'Theory of Everything
Scrunched-up dimensions untangled
The Little Book of String Theory (Science Essentials, 11): Gubser, Steven S.: 9780691142890: : Books
A GUT feeling about physics
Not Even Wrong: The Failure of String Theory and the Search for Unity in Physical Law: Woit, Peter: 9780465092758: : Books
Domenic Bahmann - Design & Art - New Scientist