The word "innermost" means the very deepest or most private part of something or someone. It refers to the feelings, thoughts, or core essence that are deeply hidden or personal. Full definition
Just as the surgeon can open up our chest and see our heart, yet she can not see the intentions or innermost thoughts of the individual who holds them. (bluemountaingallery.org)
Proxima B planet orbits about 7.5 million kms (4.6 million miles) from its Proxima Centuari star (about a tenth the distance of innermost planet Mercury from the Sun). (aerospaceguide.net)
The transverse abdominis, also known as the TVA muscle, is the deepest innermost layer of all abdominal muscles and is located underneath your rectus abdominis (the six - pack belly muscle). (fitnessandpower.com)