Disclosed is a multistage thermal convection apparatus such as a two-stage thermal convection apparatus and uses thereof. In one embodiment, the two-stage thermal convection apparatus includes a temperature shaping element that assists a thermal convection mediated Polymerase Chain Reaction (PCR). The invention has a wide variety of applications including amplifying nucleic acid without cumbersome and expensive hardware associated with many prior devices. In a typical embodiment, the apparatus can fit in the palm of a user's hand for use as a portable, simple to operate, and low cost PCR amplification device.