Here is an interesting image I found illustrating the location of follicle stem cells at different points in the hair growth cycle. I felt it was worth sharing here since having an understanding of this will go a long way toward helping one do electrolysis effectively.
The stem cells are what make the follicle capable of regenerating so they are ultimately what you must destroy if you want the hair to stop growing. It can be seen that while the bulge is the primary ‘reservoir’ of stem cells, the cells proliferate down the sheath during anagen phase.
Interestingly, it also shows that the bulb area at the base of a fully mature anagen hair is devoid of stem cells. Thus the traditional strategy of inserting to ‘full anagen depth’ would seem to be misguided, since in that case you are positioning the tip of the probe where the most energy is delivered at a place that does not need to be treated.
Also it can be seen that telogen and late stage catagen are actually the easiest to treat using electrolysis, since the stem cells are localized around the telogen ball at that point. In contrast, it is also clear why laser is best on early stage anagen hair and is incapable of treating telogen and catagen hairs, since the red part on the illustration at the base of catagen/telogen hairs has little pigmentation and will not absorb much laser energy.
This information is of particular use to DIY electrologists where you have the advantage of being able to feel where the energy is being delivered (especially when using insulated probes). I have developed several strategies for using that advantage to specifically target the repository of stem cells at the bulge to ensure that they are destroyed, since it is obvious that the stem cells there which extend away from the follicle are the most likely to survive in the case of undertreatment. I will post some info on that in another thread.
Also, see here for the article this image originates from: http://www.anticancer.com/Li-2003.PNAS.pdf