Select an Edit Poly or editable poly object. > Modify panel > Polygon sub-object level > Edit Polygons rollout > Tessellate Settings button
This dialog lets you specify how Tessellate should subdivide polygons.

Edge—Inserts vertices in the middle of each edge and draws lines connecting those vertices. The number of polygons created will equal the number of sides of the original polygon.
Face—Adds a vertex to the center of each polygon and draws connecting lines from that vertex to the original vertices. The number of polygons created will equal the number of sides of the original polygon.
Tension—Lets you increase or decrease the Edge tension value. Available only when Type: Edge is active.
A negative value pulls vertices inward from their plane, resulting in a concave effect. A positive value pulls vertices outward from their plane, resulting in a rounding effect.