The journey of vegetable crops start from the seeds and end with the new seeds. As a matter fact, we can harvest vegetables at any growing phase.
You can even consume seeds such as beans, grains, chia seeds etc. Eventhough seeds contain complex compounds, some seeds still contain high nutrients.
When a seed start growing, the very fisrt stage is germination process. Normally, it takes couple days for seeds to germinate. At this stage, the complex compounds within the seeds are broken down into simple compounds including enzymes and growth regulator components. In other words, germinated seed contains a comprehensive simple compounds, A to Z, that are required to start a new life. In fact, it is one of the best nutrients. Thats why germinated seeds, such as germinated pumpkin seeds, germinated brown rice, are one of our best nutrient sources.
When you let the seed growing, in couple days you will see the roots, and then the stems, and cotyledon leaf start appearing. At this stage, normally we call is sprouts which also contain a comprehensive nutrient thats good for us. Up to these stages, you dont need light nor soil to grow sprouts.