Sometimes, I harvest plants on my way to work, I take a razor blade and I admire #PlantAnatomy under the microscope.
For today, it is a cross section in a stem of common nettle (Urtica dioica, #Urticaceae). Several vascular bundles are joined by the dark circular cambium (that will generate wood and secondary phloem later). Inside, the pith; a part of it has been degraded. The stem is surrounded by collenchyma, a support tissue.
Of course you can recognize the large stingings hairs.