When you hear a sound you perceive vibrations in the air produced by the sound’s source. Millions of hair cells (pictured in green) lining the inner ear detect these vibrations. Each cell has tiny hair-like projections that vibrate along with the sound waves, triggering a sequence of events inside the cell to generate an electrical signal. Hair cells quickly transmit these signals to brain cells using synaptic ribbons (pictured in red), structures specialized for rapid signaling - important when that car horn is a warning to watch out.