What makes the best phone camera?

When the Visualphone VP210 hit the market in 1999, it advertised a never-before-seen feature: a camera. With only .11 megapixels, the Visualphone is a relic compared to modern devices. But while this technology has improved dramatically, engineers are rapidly approaching a hard limit on phone camera quality. So, what's limiting them? Rachel Yang shares a snapshot of how digital cameras work.