The number of mitochondria in cells is highly variable and depends upon cellular metabolic needs. The size of the organelles usually ranges from about 1 to 10 micrometers. Mitochondria were first discovered in the mid 1800s and were given their current name in 1898 by Carl Benda who coined the term from the Greek words for "thread" and "granule." The proximity between mitochondria and the actin cytoskeleton is visualized in the digital video sequences presented in this section. Mitochondria were labeled with mCherry fused to a mitochondrial targeting signal and F-actin was tagged with a chimera of mEmerald and alpha-actinin.