Each type of cell has different classification methods
All classifications used to rely on morphology, but now they are slowly moving towards molecules
Bacteria In the past, we usually looked at the morphology and divided them into bacilli, cocci, etc., or divided them into gram-positive or negative bacteria based on staining. Nowadays, we generally rely on the DNA sequence of the 16s subunit of rRNA to identify the species.
Animal cells can be divided into epithelial-like cells, fibrous-like cells, and balabala cells based on their appearance, such as morphology. . Or nerve cells that can be seen at a glance. Now we distinguish according to surface molecules. For example, if CD3 expression is determined to be T cell, it will be further subdivided into CD4+ or CD8+ and then divided step by step. The molecules on the surface of different cells of different animals are different, so they can be easily distinguished.
I am not familiar with plants, I guess surface molecules can also be used