Lets talk about the Ripening Hormone: Ethylene!
Ethylene is a gaseous hormone produced by the plant in response to cooler temperatures, shorter days and other environmental triggers. Ethylene promotes fruit ripening and plant senescence. When tomato's begin to turn from green to red, or when flowers mature, ethylene is likely a key player.
Many commercial crops are picked when they are still immature and green; like tomato's for example. The fruits are transported great distances and ripened artificially with ethylene gas. The result is fruit that looks wonderful but is lacking in flavor and aroma.