The phenomenon of Bose-Einstein condensation is a fascinating one. It occurs in several systems both in condensed matter and also in cold atomic  gases. How the interactions among the particles affect this transition is of course a very important question. In that respect, localized spin systems provide a marvelous opportunity to  study the BEC of strongly correlated bosons, since spins 1/2, or spin dimers can be  viewed as  hard core bosons. One the other hand in one dimension it is well known that spins behave more as fermions than as bosons.
Understanding the interplay between these two limit is thus a challenging  question. Recently a compound which is a good realization of ladders has been experimentally  studied and is a good playground to tackle these issues. I will thus review the above physics  of ladders and BEC in spin systems, and discuss the question of the dimensional crossover and its  experimental consequences for quantities such as the Nuclear Magnetic Resonance in such systems.