Scientific and logical description is better to use a quantitative expression, micro and nano.
In commercial use, it is better to use a qualititative expression, Fine bubble and Ultra-Fine.
But, how to use 2 expression is clearly different, and we have to discriminate between them.
And most important size is Micro-Fine-Bubble. It size is 500nm～50μm.
Micro-Fine-Bubble have a curiously power and effect.
Especially, about 100nm size nanobubble is remain in the water a long time, not less than ten
days. But, this phenomenon is not resolved.
And even more, we can not grasp what is the state of the air contained in the water?
Water is still in the mysterious and non-resolved world.