Mankind cannot survive without the nutritional and medicinal properties of plants. The number of plant species on Earth has been estimated at around 400,000, with many of these species remaining unknown to humans. While only a fraction have been identified and categorized by Western botanists, it is safe to say that many of the plants unknown in the West are known to indigenous people living within the plants' natural ranges. All ancient and indigenous peoples insist their knowledge of plant medicines comes from the plants themselves and not through trial-and-error experimentation. Less well known is that these plant teachings are at the basis of many of the modern discoveries in both medicine and in plant foods. Throughout the world there is a tradition of direct perception of nature through the "intelligence of the heart." Recent discoveries in neuroscience have proven that over 50 percent of the heart is comprised of neural cells. The heart is, in fact, a brain in its own right. Heart-centered perception can be exceptionally accurate and detailed in its information gathering capacities, as indigenous and ancient peoples assert.