Revelation 7:13 And one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?
14 And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.
15 Therefore are they before the throne of God, and serve him day and night in his temple: and he that sitteth on the throne shall dwell among them.
16 They shall hunger no more, neither thirst any more; neither shall the sun light on them, nor any heat.
17 For the Lamb which is in the midst of the throne shall feed them, and shall lead them unto living fountains of waters: and God shall wipe away all tears from their eyes.
As chapter seven closes we see an elder asking who are theses in white robes but he already knows he just whats wants to use this as a teaching session to those who may not know. Again these are the ones that accepted Christ after the rapture and martyred in the tribulation and they are constantly before the throne praising and worshiping God and the Lamb. And we also are reassured they in heaven for it says they will not need anything because the Lamb of God will be there to provide all needs and wipe away every tear.