Quarks are elementary particles that are considered to be the fundamental building blocks of matter, according to the standard model of particle physics. As far as our current understanding goes, quarks are indeed among the smallest known objects in the universe.
However, it is important to note that quarks are not fundamental particles in the sense that they have no size or shape. They are considered point-like particles, meaning they are believed to have no internal structure or extension in space. The concept of "shape" does not apply to quarks as it does to macroscopic objects.
Quarks are always found in combination with other quarks, forming composite particles called hadrons. The most familiar hadrons are protons and neutrons, which are made up of three quarks each. Quarks interact through the strong nuclear force, which is mediated by particles called gluons.
While quarks themselves cannot be directly observed due to a property called confinement, their presence and properties are inferred from the behavior of the composite particles they form and the experimental evidence obtained from particle accelerators and high-energy physics experiments.