A short field guide drawn from one chapter of Love the Frequency. Inside: the heart's own network of around 40,000 neurons — the "heart-brain," mapped by neurocardiologist J. Andrew Armour in the 1990s — in plain language; why a growing body of research suggests your heart helps colour how you think, not only the other way around; and a five-minute breathing practice to settle your nervous system. Yours free — just tell me where to send it.