Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more  or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.  [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography .  : 10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. 
In general, once steroid use stops, the testicle begins regenerating lost tissue. Studies in rats show that the process is slow and often doesn’t recover the full pre-steroid use size (although it can get very close). Leydig cell counts often remain lower than original, suggesting that testosterone levels may be reduced in the long run. In practice, the longer period you used the steroid for (or the higher dose you used), the longer time you will need for your testicles to recover. Most men are able to recover most of the lost size but may notice that they don’t get quite back to the original size, a lower baseline testosterone level or permanently reduced sperm count. This is especially true for long term or high dose users.
Although the modern doping products are very powerful in promoting muscle growth and body fat reduction, better think twice before starting to use them and inform yourself very well about their side effects and health risks. If you are hoping for a long and healthy life, you probably do not want to become a chemical bodybuilder. A must-see for everybody who considers starting with anabolic steroids is the documentary on steroids produced by Nat. Geogr. Chan. One of the best books with practical information on anabolic steroids is Anabolics by William Llewellyn.