Black and Grey style tattooing involves only black ink that has been thinned into different shades of grey. When in the early development of black and grey style only a single needle was typically used. In theory this is the most painful application of tattoo as there is less surface are for the needle penetration into the skin. Also this way of application would take much longer as only very little coverage would be achieved per hand stroke.
The style was mainly recognized in the 1970’s and typically done in prison. Now a days the style has made many advancements and new branches of the style have become accepted and popular as striking and well upholding tattoos. Larger needle configurations are used to get the job done faster and with ease. Apposed to the typically light powdery look of traditional black & grey, images are conveyed with high contrast plains. Also the use of outlines and harder edges of images have leaked its way into the black and grey category.
As for my own approach to black and grey tattooing I would consider it to lean more towards an illustrative style. I do offer portraits and imagery that has a 3-D look but it they will have my own flair and artistic touch to them.