The beginning One hundred and fifty years ago on 3 April 1858, at 37 years of age, Rudolf Virchow (Box 1) promulgated the concept of neuroglia in a lecture delivered at the New Pathology Institute of Berlin University. This lecture was part of a series of 20 lectures for colleagues and medical practitioners, and the 13th was entitled ‘Spinal cord and the brain’. In that lecture, Virchow made public his earlier thoughts [1] on the brain connective tissue, the ‘nervenkitt’or nerve-cement, which he termed ‘neuroglia’; he had coined the term already in 1856 in a comment to an earlier article from 1846 when his collected works were republished. The lecture series, however, was a landmark because it was stenographed by one of his students and published, almost without changes, in the same year. The resulting book, which appeared under the title Cellular Pathology [2], is one of the most influential medical publications in the 19th century. From there, the term neuroglia and the concept behind them spread around the world.

Already in Virchow’s eyes the concept of neuroglia was set against the concept of nervous elements; he wrote ‘Hitherto, gentlemen, in considering the nervous system, I have only spoken of the really nervous parts of it. But if we would study the nervous system in its real relations in the body, it is extremely important to have a knowledge of that substance also which lies between the proper nervous parts, holds them together and gives the whole its form in a greater or less degree’[2]. This division between nerve elements and supportive tissue still persists to a large degree in the views of many neuroscientists. For Virchow neuroglia was a connective material, although he would admit that it ‘also contains a certain number of cellular elements’(Figure 1). Nonetheless, glial elements were recognized even before Virchow’s ideas appeared when, in 1838, Robert Remak described a sheath around single nerve fibres (R. Remak, PhD thesis, University of Berlin, 1838) and in 1851 Heinrich Muller [3] discovered radial fibres in the retina (which later became known as Muller glial cells). The second part of 19th century was a golden age of cellular histology, and soon after initial findings many different forms of glial cells were described and images published, for example by Otto Deiters, Jacob Henle, Camillo Golgi, Gustav Retzius and many others [4–7]. In 1893, Michael von Lenhossek proposed the term ‘astrocyte’[8](astroglial cell), and, slightly later, Kölliker [9] and Andriezen [10] divided those