English: Light microscopic (A) and Raman spectroscopic (B) image of Micrasterias denticulata. (A) The cell consists of two semicells that are connected by an isthmus (black arrows). Each semicell has one polar lobe (PL) and four denticulated lateral lobes (LL). The nucleus (N) is located in the cell center. (B) The different colors of the Raman image represent chemically different regions identified by non-negative matrix factorization. The green color represents the cellulosic cell wall which is more distinct and thicker in the non-growing old semicell, when compared to the newly formed young semicell (upper part). In the young growing semicell, the cell wall in the area of the indentations is highlighted more intensively (arrows) than at the lobe tips.