For a long time, scientists believed that steroid hormones are produced in endocrine glands and enter into the nervous system to influence its development and function. A recent scientific discovery revealed that steroids can also be produced in the nervous system- both in brain and in peripheral nerves- independently of the endocrine organs. These are highly related to the formation of new myelin sheaths, which are layers of myelin, encasing and insulating the nerve fibres, the improvement of spatial memory performance and the modification of sleep patterns. Although their importance is very clear, little is known about their content and the roles that both types of steroids play within the nervous system. This is mainly due to two reasons: free steroids are difficult to extract and steroids come in such small quantities that are insufficient for thorough analysis. Hence, research activities concerning the characterisation of steroids and the study of their production mechanisms have been significantly resticted. Challenged by these current drawbacks, a research group developed a new microassay measurement technique for steroids, featuring high sensitivity, accuracy and robustness. This consists of the extraction of low amounts of steroids from small tissue samples, their separation by gas chromatography (GC) and their identification by mass spectrometry (MS) techniques. Compared to conventional radioimmunology, the new technique offers new capabilities of qualitative and quantitative specification of many steroids from the same tissue sample at the same time. Interestingly enough, it can precisely determine extremely low amounts (femtomols) of steroids in a variety of samples such as biopsies, cerebrospinal fluid and cultured cells. Empowered by these unique capabilities researchers can use this diagnostic tool to identify new steroid compounds in biological samples, to characterise the steroids presently found in the nervous tissue and to study their production mechanisms. Such research activity will significantly contribute to the development of new medical treatments of diseases and disorders of the nervous system.