They're mass-less, and are usually thought of as a zero-dimensional object, having no volume and taking up no space. You can theoretically have an unlimited nu

They're mass-less, and are usually thought of as a zero-dimensional object, having no volume and taking up no space. You can theoretically have an unlimited number of them in a space due to this, but due to other properties of bosons (like photons), there are other limits. In particular, if you accumulate enough of them they spontaneously spawn new particles! They aren't really physical particles in the classical sense, they cross quantum fields, and to the extent that those occupy space, the photon isn't in any one position, but merely crossing it or spread out across it.