A Drop in the Ocean is Teeming with Life : Image

Flasks with colored fluid

Flasks contain samples to be injected into a liquid chromatograph-mass spectrometer to reveal the dissolved organic carbon in them. The brown fluid in the flask on the right contains organic carbon compounds produced and released by a specific autotroph. (The left flask is a control for the experiment, containing a seawater-based incubation medium with no autotrophs added.) Some  dissolved organic carbon compounds, like the brown pigments here, can be seen with the naked eye, but most are colorless and can’t be seen without the help of instruments such as a mass spectrometer.
(Photo by Jamie Becker, MIT WHOI Joint Program)