femtograms

A femtogram (fg) is a unit of mass in the metric system equal to 10^-15 grams. In SI base units, it is 10^-18 kilograms. The name combines the prefix femto with the gram.

Femtograms describe masses at the extreme low end of ordinary laboratory scales. They are commonly encountered in fields such as molecular biology, chemistry, nanotechnology, and physics, where researchers handle very small quantities of DNA, proteins, nanoparticles, or aerosol particles. For context, 1 nanogram is 10^-9 g and 1 picogram is 10^-12 g, so a femtogram lies between attograms (10^-18 g) and picograms, being 1,000 times larger than an attogram and 1,000 times smaller than a picogram.

Measurement at the femtogram level is challenging and requires highly sensitive equipment. Techniques may include ultra-microbalances, specialized mass spectrometers, or nanoelectromechanical systems designed to detect tiny masses. Calibration and controlled environments are essential to minimize noise and drift.

In practical terms, femtograms are relevant for ultra-small samples in research settings, such as trace analysis of biomolecules, nanoparticles, or delicate mass standards. While everyday masses are typically measured in milligrams or micrograms, femtograms occupy a niche in precision measurement and nanoscale science.

See also: SI units, metric prefixes, gram, attogram, picogram, nanogram.