Contents: (Small 17/2012)

BiosensingAn inexpensive device housing communities of living cells is stabilized by C. J. Brinker, S. M. Brozik, and co-workers within a silica matrix, for cell-based environmental biosensing, as described on page 2743.Disparate cell lines (eukaryotic and bacterial) are co-entrapped, remaining viable and responsive even at intimate proximities.Furthermore, this platform is capable of fl uorescent, electrochemical, and colorimetric detection of a single analyte in a complex solution.Coupling these methods may substantially reduce the impact of interferants, opening intriguing opportunities for integrating living cells with nanomaterials and macroscale systems. Harmonic NanoparticlesHarmonic nanoparticles (HNPs), created by M. E. Jaconi, L. Bonacina, and co-workers on page 2752, label a neural rosette.HNPs double the frequency of NIR laser light, generating blue emission, while stem cells autofl uoresce in green.The coherent nature of the HNP second harmonic emission is revealed by the appearance of an interference pattern.Thanks to the complete absence of bleaching or blinking and the possibility to be excited without wavelength limitation, HNPs are perfect for long-term tracking and depth tissue imaging of differentiating stem cell structures.