The spectacular variability of microquasars has led to many efforts to classify their observed behaviors in a few states. The progress made in the understanding of the quasi-periodic oscillations observed in these objects now makes it possible to develop a new way of identifying order in their behavior, based on the theorized physical processes associated with these oscillations. This development will also help us to reunite microquasars in a single classification based on the physical processes at work and therefore independent of their specific properties (mass, variation timescale, outburst history, etc.). This classification is intended to be a tool to improve our understanding of microquasar behavior and not to replace phenomenological states. Methods: We start by considering three instabilities that can cause accretion in the disk. We compare the conditions for their development, and the quasi-periodic oscillations they can be expected to produce, with the spectral states in which these quasi-periodic oscillations are observed and sometimes coexist. Results: From the three instabilities that we proposed to explain the three states of GRS 1915+105 we actually found the theoretical existence of four states. We compared those four states with observations and also how those four states can be seen in a model-independent fashion. Those four state can be used to find an order in microquasar observations, based on the properties of the quasi-periodic oscillations and the physics of the associated instabilities.