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We propose a novel approach for efficienttuning of optical properties of a high refractive index subwavelengthnanoparticle with a magnetic Mie-type resonance by means of femtosecondlaser irradiation. This concept is based on ultrafast photoinjectionof dense (>1020cm–3) electron–holeplasma within such nanoparticle, drastically changing its transientdielectric permittivity. This allows manipulation by both electricand magnetic nanoparticle responses, resulting in dramatic changesof its scattering diagram and scattering cross section. We experimentallydemonstrate 20% tuning of reflectance of a single silicon nanoparticleby femtosecond laser pulses with wavelength in the vicinity of themagnetic dipole resonance. Such a single-particle nanodevice enablesdesigning of fast and ultracompact optical switchers and modulators. [ABSTRACT FROM AUTHOR]