  A system of two initially homogeneous, physically real fields uniformly
attracted to each other is considered as the simplest basis of the
self-developing world structure. It is shown that the system is unstable
against periodic cycles of self-amplified, essentially nonlinear squeeze of its
extended part to a small volume around randomly chosen centre, followed by the
reverse extension. The resulting spatially random pulsation, or "quantum beat",
is observed as (massive) elementary particle such as the electron. The property
of mass is then universally and consistently defined as temporal rate of such
dynamically chaotic and essentially nonlinear quantum beat, without
introduction of any additional entities. The obtained picture can be considered
as complex-dynamical completion of the "double solution" concept of Louis de
Broglie. The dynamically emerging wave-particle duality, quantum discreteness,
indeterminacy, space, and time lead to the equations of special relativity and
quantum mechanics, providing their causal explanation and explicit unification.
The elementary particle structure, its intrinsic properties, quantum and
relativistic behaviour are obtained thus all together, within the unified
analysis of the unreduced interaction process leading to the universal concept
of dynamic complexity. The same complex-dynamical process accounts for the
universal gravitation and general relativity. The electromagnetic, weak, and
strong types of interaction between particles also constitute integral,
dynamically unified parts of quantum beat processes inside elementary
particles. The classical, dynamically localised behaviour emerges in a closed
system as a higher complexity level corresponding to formation of elementary
bound systems (like atoms).
