FIELD 01GFP began as a glow inside a jellyfish and became a lantern for living cells.
FIELD 02Its strange gift is autonomy: the protein can form its own light-emitting chromophore without a complicated added dye.
FIELD 03Once researchers expressed it in other organisms, invisible biology gained a visible signal.
FIELD 04Cells could be watched while genes turned on, proteins moved, and tissues changed.
FIELD 05A marine protein became one of biology's most useful ways to see.
GFP did not just glow. It taught cells how to report from the inside.