the neutrino is considered one of the smallest known particles. It is an elementary particle with a very small mass and interacts extremely weakly with matter. The exact size of a neutrino is not well-defined since it is a point-like particle according to the Standard Model of particle physics.
However, it's important to note that our understanding of particle physics is continually evolving, and new discoveries and insights may emerge in the future. While there is currently no evidence for particles smaller than neutrinos, ongoing research and experiments, such as those conducted at high-energy particle colliders like the Large Hadron Collider (LHC), aim to explore the fundamental constituents of matter and could potentially reveal new particles or phenomena that challenge our current understanding.
It's also worth mentioning that the concept of "size" can be different when discussing elementary particles. Unlike macroscopic objects, elementary particles are not considered to have a defined physical size in the same way. Their properties are described by their mass, charge, and other fundamental characteristics, rather than a measurable size in the traditional sense.
Therefore, while neutrinos are currently considered some of the smallest known particles, our understanding of the fundamental building blocks of the universe is an ongoing pursuit, and future discoveries may shed more light on the subject.