  A state of matter in which molecules show a long-range orientational order
and no positional order is called a nematic liquid crystal. The best known and
most widely used (for example, in modern displays) is the uniaxial nematic,
with the rod-like molecules aligned along a single axis, called the director.
When the molecules are chiral, the director twists in space, drawing a
right-angle helicoid and remaining perpendicular to the helix axis; the
structure is called a chiral nematic. In this work, using transmission electron
and optical microscopy, we experimentally demonstrate a new nematic order,
formed by achiral molecules, in which the director follows an oblique helicoid,
maintaining a constant oblique angle with the helix axis and experiencing twist
and bend. The oblique helicoids have a nanoscale pitch. The new twist-bend
nematic represents a structural link between the uniaxial nematic (no tilt) and
a chiral nematic (helicoids with right-angle tilt).
