Abstract: A matroid is a combinatorial object generalizing the idea of “linear independence” of a set in vector spaces. One example of a matroid is the edge set of a finite graph together with all forests in the graph. Such matroids can be used to prove the correctness of various greedy algorithms for finding spanning trees of a finite graph. Besides this instance of matroids, I want to share with you some invariants of general matroids and their incarnations in geometry that connect combinatorics, graph theory and algebra.