Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, the bound state of an antiproton and a positron, is made entirely of antiparticles and is believed to be stable. It is this longevity that holds the promise of precision studies of matter-antimatter symmetry. Low energy (Kelvin scale) antihydrogen has been produced at CERN since 2002. I will give an overview of the experiment (ALPHA) which has recently succeeded in trapping antihydrogen in a cryogenic Penning trap for times up to approximately 15 minutes. We have also been able to flip the spin inside of the atom using microwaves, performing the first measurement of resonant transitions within an antimatter atom. Most recently, we have measured the 1s-2s frequency to one part in 5 billion. I will conclude with prospects for laser cooling antihydrogen and future precision measurements.