Tomatoes are just about everyones favorite, and the seeds from them are probably the easiest to save.
You will be better off saving self-pollinating vegetables, so the cross-pollination process doesnt get too involved.
With a self-pollinating variety, your seed will come true next year with no problems.

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The other easy seeds to save are peppers and beans.
Then, you will add fresh purified water, and shut the lid.
You will let that mixture ferment for 5 days at room temperature.

Then lay the seeds out to dry naturally.
