Germination is the way that a seed takes up water and swells, and then begins to split so that a tiny root, and then a shoot can pop out. The root comes first so that the shoot will always have a supply of water as it grows.

The shoot is responsible for making new tissues, and to do this it first uses up all the food stored in the seed, and hopefully by this time it will have grown leaves which can soak up sunlight and take over the business of making tissues.