Tactus has invented dynamic physical buttons that rise from your touchscreen. From TG Daily:

“Well, Tactus uses microfluidic technology to create physical buttons that rise from the touchscreen to give users the experience or feeling of operating a physical keyboard. When no longer needed, the buttons recede back into the touchscreen, leaving no trace of their presence. The Tactile Layer panel is a completely flat, transparent, dynamic surface that adds no extra thickness to the standard touchscreen display since it replaces a layer of the already existing display stack.”