Objective: UPlanSApo 100x oil/1.40	Exposure: 350 ms
Microscope: Olympus DSU/IX81	Gain: 3
Camera: Hamamatsu ImagEM	Interval: 2 s

The number of mitochondria present in a cell depends upon the metabolic requirements of that cell, and may range from a single large mitochondrion to thousands of the organelles. Mitochondria, which are found in nearly all eukaryotes, including plants, animals, fungi, and protists, are large enough to be observed with a light microscope and were first discovered in the 1800s. The name of the organelles was coined to reflect the way they looked to the first scientists to observe them, stemming from the Greek words for "thread" and "granule." For many years after their discovery, mitochondria were commonly believed to transmit hereditary information. It was not until the mid-1950s when a method for isolating the organelles intact was developed that the modern understanding of mitochondrial function was worked out. The digital video above displays normal fibroblast lung cells (FoLu line) from the Gray fox expressing monomeric green fluorescent protein (mEGFP) that has been fused to the mitochondrial targeting signal from subunit VIII of human cytochrome C oxidase.