Photonic crystal surfaces that can be fabricated inexpensively over large surface areas can be designed to produce optical resonances for any desired wavelength in the optical spectrum from ultraviolet to infrared. Label-free biosensing is obtained by measuring shifts in the resonant wavelength as biomaterial deposits on the photonic crystal, while the intensified electric fields that occur due to coupling of illumination at the resonant wavelength may be used to more effectively excite fluorescence or Raman scattering. Photon emitters, such as quantum dots, fluorescent dye molecules, and Raman scatters can efficiently couple their energy to detection instruments when they are in close proximity to a photonic crystal with a resonance that matches the emission wavelength. Finally, the narrowband optical filtering capability of photonic crystals can be effectively applied for infrared absorption imaging of biological specimens at discrete wavelengths. This talk will summarize recent activities in the Nano Sensors Group at the University of Illinois in which photonic crystals are used to address a variety of problems in biological sensing.