CERN Axion Solar Telescope (CAST) is an experiment probing hypothetical particles: the axions, created in the solar core.Inside the transverse magnetic field of the CAST magnet, axions can beconverted into x-rays, and be detected by four x-ray detectors atCAST. The expected x-ray signal in CAST is in 1–10 keV range,intensity depending strongly on the coupling constant of axion-photonconversion gaγ, which is expected to be low. This requiresCAST to have detectors with very low background levels.The CAST Experiment makes use of three Micromesh Gaseous Structure(micromegas) detectors, which are gaseous detectors, derived fromideas of Multiwire Proportional Chambers (MWPC). CAST Micromegasdetectors show perfect stability, good spatial and energyresolution. The intense study on Micromegas has enabled CAST tounderstand the nature of its background level, and improve it by afactor of 102 over ten years. New detector design, new readoutsystem, better cosmic veto and addition of x-ray telescope willfurther improve the background in the next data taking of theexperiment.The Charge-Coupled Device (CCD) of CAST is a pn-CCD detector with200 × 64 pixels. The CAST CCD is coupled to an X-ray telescope,focusing all the parallel x-rays into a 9 mm diameter spot. The CCDwill be replaced by the InGrid detector, a special manufacturedmicromegas detector. It is able to detect single electrons, and thelow energy capabilities will open new frontiers on search of axionsand other exotic particles. Another option is the Silicon DriftDetector (SDD), which is being tested in 2013, and has an energythreshold as low as 250 eV.The CAST experiment is the pioneering helioscope that excludes animportant part of axion mass-coupling constant parameter space, andexpects to exclude more in the following years. To succeed CAST, a newexperiment, the International AXion Observatory (IAXO) is beingdesigned and optimised, comprising the construction of a magnetspecially built for axion search as well as new detectors that willenable to improve the actual limits by 1–1.5 orders of magnitude.