Nanosensors can detect physical stimuli on the nanoscale and are being developed for use in medicines. Common nanosensor materials include porous silicon, nanoparticles, and nanowires. Porous silicon has a nanostructured surface that can absorb and emit light, making it useful for optical sensing applications. Colorimetric gold nanosensors can detect medicines by measuring changes in localized surface plasmon resonance signals as nanoparticles aggregate or bind ligands on their surface. Nanoprobes like PEBBLE sensors can detect chemicals inside single living cells. Nanowire sensors functionalized with molecules like aminopropyltriethoxysilane can detect pH changes electrically. These nanosensors show potential for applications in the pharmaceutical industry.