HBT: A (mostly) experimental overview

I will present a review of the field of Hanbury Brown-Twiss interferometry in relativistic heavy-ion collisions. The "HBT puzzle" is explored in detail, emphasizing recent theoretical attempts to understand the persisting puzzle. I also present recent experimental results on azimuthally sensitive HBT, HBT of direct photons, and some surprises in the comparison of HBT results from p+p and Au+Au collisions at RHIC.Comment: 8 pages, 3 figures. Proceedings of the Quark Matter 2004 conference (Oalkland, CA, USA, January 2004