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Making an object "invisible" means cloaking it from detection by electromagnetic waves in the optical wavelengths (380-750 nanometers, equating to frequencies of about 790-400 terahertz). Liu et al., using "transformation optics" and special metamaterials, designed a cloak that operates at the gigahertz level and can cloak objects beneath the bump. The animation shows the incident radiation (from top) traveling across a flat conducting plane, striking the bump, and then reflecting off at the same frequency, thereby effectively concealing the bump's presence. The results, according to the report, should scale well to optical wavelengths.