Miniature spectrometers could make it easier to perform spectroscopy on the go. Jie Bao of Tsinghua University, in Beijing, and Moungi G. Bawendi of MIT have now developed a new way of creating one from an array of 195 filters made by printing different colloidal quantum dot inks on a microchip (Nature 2015, DOI: 10.1038/nature14576). The spectrometer, which covers the wavelength range of 390 to 690 nm, is the size of the charge-coupled device (CCD) sensor in a digital camera. Because each filter transmits light differently at different wavelengths, the intensity of light transmitted through the set can be combined to reconstruct the spectrum. Bao and Bawendi used their spectrometer to measure spectra generated by a white light source and a set of optical filters and to measure the emission spectra of fluorescent colloidal quantum dots. The researchers were able to resolve spectral peaks separated by 2 to 3 nm. They say the spectral range and resolution could be further improved by using additional quantum dot filters.