Hugo von Mohl made noteworthy advances in cell microscopy, plant microanatomy, and cell physiology. Mohl was born into a prosperous, intellectual family in Stuttgart, Germany. He showed an early predisposition toward both optics and botany, and became an expert microscopist while still a teenager. He earned a medical degree at the University of Tübingen in 1828 with a dissertation on plant pores. After four years of postdoctoral botanical research at Tübingen, at the University of Munich, and in the field, he was professor of physiology at the University of Bern, Switzerland, from 1832 to 1835 and professor of botany at Tübingen thereafter. At Tübingen he also directed the botanical gardens, founded in 1837 the Herbarium Tubingense, which in 2001 contained over a quarter million cataloged specimens, and co-founded in 1843 a major journal, Botanische Zeitung. He died peacefully in Tübingen.

With no clique of either students or colleagues, no wife or children, and no serious personal upheavals, Mohl led a singularly uneventful life. He was absolutely dedicated to his work, to which he brought technical skill, imaginative thinking, and rigorous empiricism. In writing, he just reported his observations clearly and directly, and refrained from drawing conclusions. He reacted strongly against German romanticism in general and the nature philosophy of Friedrich Wilhelm Joseph von Schelling (1775-1854) and Lorenz Oken (1779-1831) in particular. Both his anti-speculative philosophical stance and his lifelong scientific achievement foreshadowed the positivism that, in the wake of Auguste Comte (1798-1857), would dominate Western European thought throughout the latter half of the nineteenth century.

Mohl may have been the first to distinguish the cell wall from its contents. Matthias Jacob Schleiden (1804-1881) and Carl Wilhelm von Nägeli (1817-1891) pursued this line of research further. From his studies of algae, Mohl originated the hypothesis that cells reproduce by dividing. His most important discoveries are contained in his long article, Die vegetabilische Zelle(The vegetable cell) in Rudolph Wagner's standard 1853 reference work, Handwörterbuch der Physiologie (Dictionary of Physiology).

The Czech physiologist Jan Evangelista Purkinje (1787-1869) coined the term "protoplasm" in 1839 to apply to the embryonic substance of egg yolks. In 1846, Mohl used this name for the colloidal and granular complex of living substances in cells. Max Johann Sigismund Schultze (1825-1874) more narrowly defined protoplasm in 1861, but the concept of protoplasm in cytology is forever associated primarily with Mohl.