A single vortex in a type-II superconductor: order parameter ψ(r) ≈ tanh(r/ξ)·e^(iθ), where ξ is the coherence length. The vortex core (|ψ|=0) has size ξ, magnetic flux penetrates with London length λ. GL parameter κ = λ/ξ determines type-I (κ<1/√2) vs type-II (κ>1/√2).