The long-standing "Kaonic-helium puzzle", i.e., the discrepancies between the
measured and calculated strong-interaction shift of the 2p-level of kaonic
helium 4, has been solved by the KEK E570 experiment; the measured 2p-level
shift was 2+-2(stat.)+-2(syst.) eV, thus agreeing with a majority of the
theoretical calculations. The 2p-level width was also found to be small 
(< 17 eV). The smallness of the kaonic helium-4 2p-level shift has recently been
confirmed by the SIDDHARTA collaboration at DAPhiNE. Both of these experiments
have used state-of-the-art silicon drift detectors (SDDs) as the X-ray
detectors, and have used elaborate in-situ calibration methods. In order to
further study the low-energy kaon-nucleus interaction, the SIDDHARTA
collaboration has also taken some kaonic helium-3 data, and the J-PARC E17
experiment will soon measure the kaonic helium-3 2p-level shift and width to
high precision. Implications of these measurements on the study of kaon-nucleus
bound states will be discussed.