  The study of fundamental properties (such as temperatures, radii, masses, and
ages) and interior processes (such as convection and angular momentum
transport) of stars has implications on various topics in astrophysics, ranging
from the evolution of galaxies to understanding exoplanets. In this
contribution I will review the basic principles of two key observational
methods for constraining fundamental and interior properties of single field
stars: the study stellar oscillations (asteroseismology) and optical
long-baseline interferometry. I will highlight recent breakthrough discoveries
in asteroseismology such as the measurement of core rotation rates in red
giants and the characterization of exoplanet systems. I will furthermore
comment on the reliability of interferometry as a tool to calibrate indirect
methods to estimate fundamental properties, and present a new angular diameter
measurement for the exoplanet host star HD219134 which demonstrates that
diameters for stars which are relatively well resolved (~> 1 mas for the K
band) are consistent across different instruments. Finally I will discuss the
synergy between asteroseismology and interferometry to test asteroseismic
scaling relations, and give a brief outlook on the expected impact of
space-based missions such as K2, TESS and Gaia.
