Mirkin invented spherical nucleic acids (SNAs) -- gold nanoparticles densely coated with a radial shell of oligonucleotides -- and their 'nanoflare' derivatives, which enter live cells without transfection agents and light up sequence-specifically upon binding intracellular mRNA, enabling live-cell gene-expression biosensing, circulating-tumor-cell isolation, and simultaneous mRNA detection/regulation. This label-based intracellular biosensing platform is offered as a borderline but well-established inclusion under the biosensing/dye-based imaging criterion.