Remote sensing in the optical spectrum of the biosphere takes advantage of the same atmospheric transmission windows that life itself has so successfully exploited. By measuring the radiation exiting the top of the atmosphere and accounting for the scattering and absorption characteristics of the atmosphere, we are left with the reflected radiance of the surface (land and oceans) where clouds and their shadows do not obscure the view. Scattering and absorption by the surface, as well as topographic illumination differences, modify the radiation. For vegetation, the reflectance is first altered by cellular and molecular processes. Waxes produce specular reflectance, cell walls produce diffuse scattering, and cell contents produce absorption. A similar process occurs in water by micro-organisms such as phytoplankton. Reflectance of whole canopies cannot be explained by leaf properties alone; multiple scattering, shadows, soil signatures and other objects also contribute. The first optical instruments were optimized to measure the strong contrast in vegetation between IR and visible, giving rise to time series of global maps related to capacity to absorb visible light for photosynthesis. Spectroscopic observations have never been available from space, but offer new opportunities for analysis. For plants, a look at their biochemical properties at a regional scale is possible. For oceans, various absorption pigments and organisms can be observed, especially important for highly productive coastal waters. An innovation Ames is working on is imaging interferometry, an instrument to measure the spectral continuum with high signal to noise at low cost, size and weight. Outside the optical, thermal and microwave observations have also been developed that mainly, in the latter case, measure macroscopic characteristics of vegetation, structure that organizes water in various forms.