According to our current understanding in physics, the building blocks of the universe are often described as elementary particles. These particles are entities that possess properties such as mass, charge, and spin. Examples of elementary particles include electrons, quarks, and photons.
However, it's important to note that at the quantum level, particles can also exhibit wave-like behavior. This phenomenon is known as wave-particle duality. In quantum mechanics, particles are described by wave functions, which mathematically represent the probability distribution of finding a particle at a particular location or with a particular property. The wave-like nature of particles is evident in phenomena such as interference and diffraction, which are characteristic of waves.
Moreover, energy can also be associated with waves. In quantum field theory, which is a framework that combines quantum mechanics and special relativity, particles and their interactions are described by fields. These fields can be thought of as underlying entities that permeate all of space and time, and their excitations give rise to particles. The energy of these fields is associated with the wave-like nature of the particles they describe.
So, in a sense, both particles and waves are involved in our understanding of the building blocks of the universe. Elementary particles can exhibit wave-like behavior, and the energy associated with these waves contributes to the properties and interactions of the particles. The precise nature of particles and waves in the fundamental structure of the universe is an active area of research in physics.