They are a quantised wave in the electromagnet field. The concept of shape or object size breaks down at this level.

Some scientists refer to them as point like, since we can’t measure any diameter on them. It’s more likely tied to their current wavelength. The faster they move, the more energy they have, and the shorter the wavelength. The shorter their wavelength, the smaller they are. Unfortunately this is also a vector (speed and direction) so their shape is different depending on the direction you measure them. Even more confusing, relativity comes to play too. Their velocity is different for different observers, therefore their apparent size is different.

Most experiments don’t bother dealing with this however. They just assume it’s point like, and that seems to align very well with experimental results.