There is no peer-reviewed scientific evidence that crystal healing has any effect; it is considered a pseudoscience. Alleged successes of crystal healing can be attributed to the placebo effect. Furthermore, there is no scientific basis for the concepts of "chakras", being "blocked", energy grids requiring grounding, or other such terms; they are widely understood to be nothing more than terms used by adherents to lend credibility to their practices. Energy, as a scientific term, is a very well-defined concept that is readily measurable and bears little resemblance to the esoteric concept of energy used by proponents of crystal healing.